How long of a trailer is too long?

I am looking at toy haulers. We have seen some things we like that are a bit bigger but we know bigger isn't always better with RV's. We're looking at toy haulers but it will be for general camping use as well. The first unit we looked at was listed as a 21 foot model but hitch to bumper is 27 feet. We prefer the next size/model up. That unit is called a 25 foot model but is actually 31 feet from hitch to bumper. We are concerned about getting into campgrounds with whatever we choose. We are located in northern California and most of our camping will be in California, Nevada, Oregon, Arizona areas. Just getting into the RV so we don't really know about any specific campgrounds we will be going to. Just looking for advice on size. We wouldn't want to get the smaller one if it doesn't help much on getting into sites. It seems there are so many massive RV's on the roads but then so many restrictions on sites. Just relying to figure out what people are doing? The toy hauler will be set for boondocking with 100 gallons of fresh water and a generator so we wouldn't need the hook ups all the time.