We have done the NW twice. SPs & NPs are our preference. Both times no reservations anywhere.
Sunday to Thursday is easy most places. Weekends at popular SPs & NPs can be hit or miss. Weekdays we try to be where we want to be by mid afternoon. That way there is time for plan B if A is full. Very rare. Weekends we arrive where we want to be Friday, maybe Thursday if we think the CG will be a busy one. Stay put till Sunday, maybe Monday.
4th July. Make reservations as soon as you can. No need to be months in advance. Even as late as the week before a spot can be found in a private CG. Hole up for the holiday & let the camper storm blow through.
Push comes to shove there is always a Walmart.