My dad had an Akita and he and a friend traveled to shows with at least 2 akitas, a brittany and a rat terrier. He started with a toy hauler - it fit the kennels well. However it was awkward for two to three people not in a relationship to share.
He then went to a 5er with bunks up front, then the LR/kitchen , then bath, and then the bedroom at the back. It worked better for the people. They removed the bottom bunks and put the crates there and his friend slept in the upper bunk(s). The crates just fit under the top bunks, I can tell you it was h@11 getting them out (I somehow got stuck with that job).
My advice (after watching my dad), is if you kennel, measure the crates and do your homework and measure the RV to make sure they fit - measure twice and all that. And watch for lips, ridges, turns, etc., that could impede the crate going in or out.
I have two dogs (85 and 65lbs) and we are quite content in our 21ft C. But they are couch dogs and sleep on the bed (I have a set of dog steps for them to get from the couch to the cabover bed). If all 4 large dogs sleep on the bed, I would get a dedicated bed below (not the cabover) for simplicity and potential weight issues.
With two dogs, the floor space isn't an issue. They can both sit in the cab seats to watch what's going on. While driving, they rotate between the passenger seat, couch, dinette seat, and floor - usually picking one spot each and then moving after a stop. And they can get around each other with minimal issue on the floor. With 4 dogs you may need more floor space just so they can get past each other without an argument and you may want more "sitting" space for them so they aren't always taking up that floor space.
You're not really going to be able to bring the dogs with you while you look, but I suggest bringing a few buddies - that will help you get a feel for how the dogs will have to interact to get around. Congestion at the door can be dealt with, but you want to minimize congestion in other areas.
Also, consider where you'll feed them and put their water. Some dogs can eat right next to each other - some need more space.
Also remember that a lot of campgrounds and RV Parks don't allow you to tie up the dogs outside while you're inside - so don't count on that to ease a tight place.
As I write this, I would look for something with an open floor LR/kitchen area and a bedroom on either side of that. A slide in that center area will be far more important than in the bedroom. That gives the dogs a place to lay on the floor without blocking a narrow corrider. You could put two in each bedroom