In Oregon yes 35' will limit you. You will still find spots but they're going to be harder to get since everyone and their dogs out camping. 25' is a great length that will get you in more spots more often.
I have a 31' plus a long bed truck I need a minimum of 42' to get both in a spot. I can hang the rear of the TT over the end if needed.
Finding spots that long are easy, but finding them open is another thing. Not every campground is full of long sites. Usually it's a mix of short and long.
Most all RV parks can handle a 31-35' trailer. It's going to boil down to where you want to camp as to how easy it will be to get a spot.
I would suggest doing a hypothetical reservation plan and see what places you could actually get into when you need to.
