Going north to south, to see Oregon, one has to decide highway 101, I5, 95 or 395. Each is very different. 101 is an easy drive down the Oregon coast and, allow at least week to 10 days. One could easily spend 2 weeks looking at lighthouses, wandering in towns and checking interesting sites or even riding the sand dunes. I5 gives you all the rural areas and urban cities with funky Portland, wine tasting, museums, etc. 95 gives you the Cascades on one side and high desert on the other. If you like volcanic mountains, rocks and desert you'll enjoy 95. You'll enjoy the greater Bend area. 395 gives you the desert with interesting desolute mountains, but don't expect a lot. Not much different than most of Nevada. Don't miss the Columbia River Gorge, particularly from Portland to the Dalles.
Going across Oregon, west to east, except for I84 is all 2 lane twisty roads and slow going. Going from 101 to I5, on any of the routes allow a couple of hours. Easiest drive is 20 from Newport with the new highway. Going from I5 to 95, again allow for a couple of hours, and you'll be climbing over the Cascades. And, from 95 over to 395 will be about 3 hours, and boring. 26 is more scenic, 20 is faster, but boring and 140 is really boring!
There are some highways to avoid - 242, the Mckenzie Pass Hwy (DO NOT drive the motorhome); 199, Grants Pass to Crescent City (CA doesn't permit motorhomes over 40' on this route)
And, look for us when you're at the Ballon Fiesta. Both Lee Ann & I and Rick & Terri Mayer are going to be there with Fantasy 10/12 to 16.