Not sure what you're driving but keep an eye on the roads you want to travel. Many in PNW have length, weight, height restrictions. Like McKenzie River in OR. Cell reception through out OR can be really spotty.
My fav boondock in all of Oregon has no views. lol South of Sisters is a rodeo grounds, nestled next to NF. It isn't scenic but it is clean, 2 weeks free, great cell and within five to 20 mins drive of vital services. It is within two miles to 60 of the most awesome places to explore. Each year we stop in there a couple times so we can get repairs, big deliveries, stock up, get business done and explore. In fact, it is the only location where we had a vehicle and medical OH CRAP situation where the local law enforcement came to our rescue--In 30 years on the road. The ONLY place law enforcement ever offered us help.
Sisters is a tiny, artsy town. Adore the people there. Best biscuits and gravy I've had in 30 years of US and Canada travel can be found there. South of the NF boondock area is Bend, 20ish mins east is Redmond.
Not sure what parts of OR you're doing. Some rangers for BLM and NF are kind people, others are hardball, hand on their gun entire time you converse with them. The NF dispersed camping areas near Bend are severely abused and the rangers are not happy about it. Same for some of the BLM areas east of Bend, although I do like OR Badlands blm for short periods.
Valley wise I don't have suggestions. There is so very little area there open to dispersed and even the campgrounds can be questionable.
Coast wise, I'm not familiar with the areas north of Lincoln City. But south of it all the way to Coos Bay are a lot of NF campgrounds right on the coast. They do charge. Many have no services like water. Some are FCFS but most with Covid now require online reservations. Check first! For a van or small (under 15ish ft) trailer, these can be a great way to see the coast. Fees range depending on location and your pass. For us it is 50% off, so some campgrounds are $5 and some with electric are $19. Below Coos Bay there aren't many BLM or NF areas available. Only one I can think of is the one off Hwy 101 on the Sixes river, north of Port Orford. I think it is still a free spot. Check. But it is a great spot to get out and see things from Bandon down to Brookings, imo, if you're not wanting to pay a big state or private campground fee.
Oh, and there are some marina spots that allow vans or even tents. Winchester Bay's Salmon Harbor has one, with coin op showers, FCFS, next to the dunes and on the bay, dry dock, $17 a night or $300 a month. Does get noisey due to OHV/ATVs.
Most of the coast right now seems to be campfire okay but that changes. Every summer they ban it.
I'm sure I'm forgetting some places. Will post if more come back to me.
