Yes. Almost everything in eastern Oregon is 2 lane, with the exception of I84 and some stretches through town (Bend, Ontario). There are some passing lanes, especially on uphill stretches. But in most cases, traffic is light enough that there isn't a need for enhancements.
Google Maps streetview lets you count the lanes on almost any paved stretch in the country.
Tripcheck reststops
According to Tripcheck, both 26 and 20 have 4 rest stops.
I also don't think there are enough hills (east of US97) to worry about pulling over. Nor is traffic very heavy. US20 is somewhat flatter.
When crossing the Cascades both have passing lanes where needed on uphill stretches.
To use a Wisconsin analogy, avoiding most state highways in Oregon because you afraid of holding up traffic is like staying away from Door County for the same reason.
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