The Everest has a standard bench dinette or optional U-shaped. Although the two of us like the U, I can see how it might be tight for four adults and the traditional dual bench would make more sense.
The difference with the Mammoth is a 3-panel door to the bath that gives you more space plus the bath is a little larger than the Everest. I don't remember if the Yukon is more like the Everest or the Mammoth. Some people do not like the multi panel door and have come up with other screens for the bath while preserving knee/leg space. The swing door would be an issue for me due to long legs, but my wife could fit either.
The basement will actually fit four 27-gallon bins if you do not have an off-grid package. The tray is sturdy enough to lie on and pull yourself in to inspect or repair anything along the inside walls. My shoulders are too broad to turn over but I can get over 60 degrees rotation either direction and can lay on my chest to reach all the way to the gray tank false wall.
You will find it is few stairs to get in and out of the camper. Host's come with one internal step and 4 external steps but really need 5 outside for a pickup and 6 for a chassis cab. The most stable solution is replacing the fold up steps with a Torklift model but those do not work as well when the camper is offloaded and low to the ground. You will need to figure out how much you use the camper off and on the truck to figure out which stairs are better for you.
Once inside any of the campers that have the floor starting above the pickup bed rails (Chalet, Eagle Cap, Host), you will notice two things: First there is much more open floor space since the floor is 8-8.5' wide, Second the height transition to the cab over is more like a residential bed.
We use a fitted sheet on the residential-sized mattress and a comforter with duvet over the top. The trick is to start at the head of the bed and work your way down for each layer you apply. The cab overs in these large campers are tall enough that you can crawl around on your knees without ever getting close to the ceiling.