Using I-10, I have never stopped here, but have been tempted to do so, Caverns of Sonora, they say is a National Natural Landmark, a unique cave located 8 miles west of the town of Sonora, Texas, and a world-class cave. It does have camping as well.
The Museum of Western Art near Kerrville is really good, a must see for sure if possible.
http://museumofwesternart.com/ Should be easy to find RV sites as well. Used to be a state park by the river, but not a state park now.
I found Cascade Caverns at Boerne to be extremely neat (my first cave) when I was about 12 or 13. Not sure how it would hold up now for me.
An Old Post on Texas Hill County
The Caverns of Sonora are one of the most beautiful caves I've been to. I had a great tour & highly recommend a visit for those interested in caverns. Some photos from my visit.
If you are near Deming, NM, I suggest spending a night or two at the City of Rocks State Park. I prefer the dry sites among the rocks, but there is a section with water & electric. The campground has bathrooms with showers.
Like most parts of the country, there are many summer "Festivals" scattered around upstate NY. Whether or not you want to attend them depends on how comfortable you are with dealing with crowds, but during them they do fill up local campgrounds.
A couple that I've enjoyed include Spiediefest, a food & hot air balloon festival in Binghamton, NY (Some of my photos), Harborfest, a weekend festival culminating in an excellent fireworks display (Some of my photos).
I have also enjoyed Sunday lawn concerts at the Sodus Point Lighthouse.
There is something to do every day just about anywhere in upstate NY during the summers - a Google search for NY Summer Festivals will highlight what is available on the large scale, stops at local Visitor Centers will help find the smaller ones.
You might want to check out Babcock State Park. Electric only (bathrooms with showers) first come sites. The campground is a couple of miles from one of the most photographed mills in the state - the Glade Creek Grist Mill:
For those interested in more information about Color Temperature (the Kelvin rating of light sources) this Wikipedia article is fairly non technical & accurate.
It also includes basic information (and a link to further info) about CRI, which is a measurement of color accuracy of a source.
Last winter there was plenty of open space within 500' of the vault toilets at both LaPosa (80 miles from Yuma) and Imperial Dam (about 30 miles from Yuma). Pilot Knob is the closest LTVA to Yuma (about 7 miles), however I don't believe it has toilets so you would not meet the BLM requirements for that location.
The quote from the BLM that includes info on the different areas:
a. In Pilot Knob, Midland, Tamarisk, and Hot Springs LTVAs, you may camp only in self-contained camping units. The La Posa, Imperial Dam, and Mule Mountain LTVAs are restricted to self-contained camping units, except within 500 feet of a vault or rest room.
b. Self-contained camping units must have a permanent, affixed waste water holding tank of 10-gallon minimum capacity. BLM does not consider port-a-potty systems, systems that utilize portable holding tanks, or permanent holding tanks of less than 10-gallon capacity, to be self-contained."
NY 104 is another east/west alternative if you are heading to northern NY. 2 lane for much of it with the only hassle being Rochester. Lots of nice state parks along Lake Ontario.
US 20 is another alternative, however lots of small towns & rolling hills.
You mentioned photography - in the Blanding / Natural Bridges area there are two great photo opportunities. House on Fire ruin is in the south fork of Mule Canyon on UT95. You have to hit it at the right time of day to get the "fire" color - 10:45AM worked for me:
Another ruin that is a bit more difficult to get to is Fallen Roof Ruin. The canyon is off Cigarette Springs Road, which is about 15 miles south of the UT95/UT 261 intersection.
I have 195 watts of solar on the roof & carry a 160 watt portable panel. No generator. The rooftop panels provide all the power I need during the summer; with the shorter days & low angle sun in the winter, I need to add the portable.
I have a 1000 watt inverter to supply limited AC for making coffee, toast, etc. I avoid temperatures that require running the air conditioner, however the few times I needed it, I headed to a campground with hookups.
I spent last winter at the LTVA in Quartzsite; 93 days without hookups.
Escape 17B. With options and full fresh water about 3,000 lbs. Having said that, most people prefer to not tow quite so close to the limits.
I towed an Escape 17B (loaded weight 3010 lbs) 77,000 miles with a 2010 RAV4 Sport (V6 & Tow Package), including mountains in both the East & West. I do stick to secondary roads when possible, and generally do not tow over 60MPH. Love the trailer, and if you are ordering new, an available option is a upper bunk in front - 2 kids are not a problem. There is one problem - they are quite popular - the factory is back ordered for a year...
I spent 2 weeks camping in the Leadville area at Turquoise Lake & Camp Hale between 9500' - 10,000' . No problems with the furnace (it was down to the low 30's at night even in August), refrigerator or water heater. The fridge was an older non electronic Dometic RM2510...
You will get some great nighttime sky photos at that altitude!
One of my favorite state parks for Fall colors is Ricketts Glen in PA. 22 waterfalls along a 7 mile hike. One of the campgrounds stays open all winter - no hookups, but bathrooms with hot showers.
Some photos from a few of my visits.
I agree that there is no good way. My solution (heading to upstate NY) is to take MN 61 in Duluth into Canada & loop around the top of the Great Lakes. A pretty drive & far more enjoyable than fighting the Chicago traffic.
We stay strictly at public camping locations, including boondocking spots, and have found that The Ultimate Public Campground Project has by far more of them than any other app, including Allstays.
That's not true at all. They have almost none of the campgrounds out west. Do you work for them?
I've used both apps (Allstays Camp & RV & The Ultimate Public Campground List) for many years & over 800 campgrounds all around the US & Canada. I don't work for either, but there are advantages to each.
Allstays has many additional features including low clearances, individual store chains, even covered bridges, and an easy to use filter. On the other hand, I find that The Ultimate Public Campground List DOES have more non commercial sites in their database than AllStays, even in the west (particularly county & city campgrounds), and the map reacts faster to changes in scale. I don't like its filter as much as the one in AllStays, and it does not have as many extras. One additional advantage of the Ultimate Public Campground List is you can purchase a POI list that can be loaded into a GPS.
My suggestion is to purchase both (if you use non commercial campgrounds) and experiment to see which you prefer. Both are inexpensive, and complement each other.
While it might be a bit tight for your requirements, I have an Escape 17B - the front table converts to a single bed & there is an option for an additional upper bunk in front (150 lb limit), & a 48" rear bed/dinette.
Wet bath with shower, and many options available. The biggest current problem is there is a 14 month waiting list to purchase since they are made in Canada & the exchange rate is very favorable for US buyers.
Loaded for a long trip it is at 3100/345 lbs - for 5 years & 77,000 miles I towed it with a RAV4.
I use AllStay's Camp & RV most of the time & The Ultimate Campground List for non commercial locations. Both are available for Android & iOS, and both can be used at their websites for free. The each have filtering that lets you search for specifics.
Win 10 is no longer called an OS, it is a service. You continually pay for a service. That is the direction they are leading the sheep. They did not update Win 7 computers to 10 for free because they wanted to reduce profits.
Many of the programs are going to "monthly service" instead of buying the disk or download the program -- Adobe, for example. It forces the photo guys that use Photoshop to pay a monthly fee now, and if you stop paying, you lose the ability to process photos.
I'm not positive about this statement, but I believe in order to use the program while processing, you have to remain on the 'cloud', which means online the entire time. IF that's true (and if it isn't now, it will get there eventually) then any photo guy with limited hotspot data plan (like myself) will eat that plan alive each month.
We're on three PC's with Win7 on all - will never update to Win10 until that "warm place" freezes over. Letting MS into my PC whenever it wants, well, that ain't gonna happen. Period - at least not with me knowing it ...
Adobe's Creative Cloud requires you go on line to the company once every 90 days. After being off line for more than 2 weeks, you get a message letting you know that it hasn't "talked" with your computer. It does not automatically update your software, but lets you know when updates are available, informs you what the update covers, and the size.
The products operate off line with no problems. Although I have not tried going the full 90 days without contact, I used Dreamweaver, Photoshop & Lightroom as well as a number of their other cloud based products while not connected to the internet for weeks at a time.
As to the subscription replacement for yearly updates, I have mixed opinions. I do like the updates & "fixes" that happen more often with the subscription service, and with the amount of Adobe software I use, don't spend more with the Creative Cloud than I did with annual updates of the past, but I have to admit I cringe at the thoughts of the service disappearing. I do keep copies of the last non subscription releases of all the software, but as the new features come along, going back would be tough.