There is one pretty good climb leaving Arcata but as I remember it is 4 lanes to the top after that a good 2 lane road to Redding. It is narrow in spots and curvey it is not a route to make time on but none in this area over the mountains are we have done it a number of times in a 35 ft. MH+toad. It's a pretty drive. Have fun
I live off 299 just west of Redding. As mantioned Buckhorn summitt about 30 miles west of Redding is the worst part (uphill and twisty). Just follow the speed suggestion signs and you'll do fine. Plan on 3+ hours, or longer if you stop at the rest stops, from I-5 to 101. You will go from 100 degrees in Redding to 65 degrees on the coast. I call it the shorts to sweatshirt run.
2000 Monaco Windsor 40'
2004 Honda CRV, Unified Tow Brake