Overnighting in some states is legal and in some isn't. There is a state by state list
here. Some states also have a max. stay limit ranging from 3 - 24 hours.
Casinos are a great place to overnight and many are extremely clean & tidy and can have full services, and some with all 50 amp sites. Some charge and some don't. Some have a shuttle service. Good place to have a decent priced buffet meal - well usually at least. :(
Truck stops might seem like a possibility but truckers don't want RV-ers taking up spaces like mentioned
here. RV-ers are welcome at some truck stops though - Flying J, Loves & Pilot for example. Check with each truck stop ahead of time before stopping at one. Some truck stops are humongous, like one I've been to in CA is like an international airport. Way cool! Don't forget your earplugs...
There is an app "Allstays Camp and RV" that is supposedly good for finding places to overnight and also tells you where to find gas stations, stores, low clearances, CGs, etc.
I'd suggest having a computer and a Verizon (or other) mifi so you can get online anywhere instead of having to resort to CG wifi. Besides being able to look up places to stop, you'll be able to check out routes for construction delays, road condition, dump stations, etc. and where you might want to stop for a little sightseeing.
I'd also add be prepared to alter your route at any time due to forest fires, hurricanes, floods, etc. This summer has been pretty bad for fires in the PNW. Climate change is creating some severe and unpredictable changes in weather patterns across NA.