Re: size limits
It depends on how developed the particular Park is. The National Forest Service frequently limits size and slides. They are situated in the forest in campgrounds that were constructed many years ago and most don't even have dump stations.
National Parks often are developed and have all facilities and can accommodate all sizes. Each Park has different policies and some are run by contracted commercial services. They generally are more expensive.
State parks vary by State. Some have electric/water only. Some have Full hookups, and some only have dump stations.
Most State parks are newer and can accommodate most sized RV's.
Bottom Line: Most Parks out West can accommodate most sized RV's with the exception of Forest Service Campgrounds located in the National Forests. The BLM and Corps of Engineers also operate good campgrounds. Most Nat'l campgrounds are lower in price to camp than the commercial parks with the exception of Nat'l Parks that are operated by commercial contractors. If you are over 62 and have a Golden Age Passport the camping is generally 1/2 price with again the exception of commercially run campgrounds in Nat'l Parks.
