Travel trailer owner here.
Yes, we use the trailer all the time when traveling. Many, many times we've pulled into a parking lot, run into the local McDonalds or whatever, brought the food back out, opened the awning, pulled out a couple lawn chairs, our folding portable table and enjoy a Big Mac. It only takes a minute to set it up, and only a minute to put it all away. We do this a lot!
We do not have a generator in or trailer, but do have access to the gas stove, full access to the refrigerator, bathroom, bedroom, and living room with slides in. The only thing restricted from enjoying is the television in the living room with slides in. But the one in the bed room is just fine!
So, when traveling, if we fix our own meals, we have water on board and use the on-board water pump. We can heat stuff on the gas stove, and of course, cold stuff in the refrigerator. When we do this, we try to find a city park rather than a Wall Mart parking lot (too hot in the sun). We also have an outside (built in) gas stove, so we can always heat and cook outside if the inside is too hot.
Overnighting? We don't boom dock. We don't do Wall Mart overnights. We always stay in KOA or Good Sam campgrounds that always have full hook-ups (water, electric, and sewer). Unless the camp site is horribly unlevel, we don't unhitch, but I do put the trailer stabilizer jacks down for stability and to make sure when the 3 slides are deployed, they wont' get into a bind or anything.
Yes, if traveling all day, with no air conditioner in the trailer, the inside of the trailer can get pretty roasty hot. But with electricity, it doesn't take too long to cool things down. In the winter to create a quick heat, I'll turn on all 3 burners on the gas stove for about 10 minutes. This warms up even the coldest campers in a hurry, and by then the furnace has had a time to warm up and start pumping warm air. Then the burners on the stove are turned off (like I say, maybe 10 minutes. The stove is run longer than than when fixing eggs for breakfast).
Sometimes, if doing an overnight in a specific planned campground, we will unhitch so we can take the truck and site see or go to an event in the area. Hitching is so easy, after doing it for 50 years, I don't think anything about it any more.
About using the bathroom when traveling. Yes! We do it all the time. We NEVER use fuel station bathrooms! Never any more when the trailer is with us. That's the one advantage of having your own bathroom with you, and why it's so important in your selection of camper to make sure EVERYTHING is accessible when the slides are in.
We also use the camper in our driveway all year round too, until temperatures reach about 20 degrees F or below. So, between the end of December and the middle to end of February are about the only weeks we don't use the camper.
We slept in the camper every night now (driveway, or camping in a State Park), every night now since the March 1 of this year. We are in it right now, and will be sleeping in here again tonight.
Whatever RV you end up selecting, just make sure everything is functional when the slides are in: Bathroom door opens; kitchen sink, refrigerator, and stove are usable; bed are 100 percent usable. If you have more than just husband and wife sleeping in the camper, make sure your guests (or kids) can access their beds too with no problems with the slides in also. There will be times you'll need to use your camper (no matter what you get), when the slides need to be in.
Example: extreme cold or hot weather, to reduce the square footage to better heat or air condition the livable space. Horrible bad weather when it's howling and blowing so hard, it feels like the camper will blow over. Pulling in the slides helps reduce the surface wind-sail and we've slept in ours many nights with all the slides in because it was howling so bad outside. Sometimes you will be traveling, and will be parked somewhere it's absolutely NOT possible to extend the slides. Sometimes, at home - depending on your parking conditions - you might not be able to deploy the slides to load or unload the camper. Yes, there will be times the slides need to be in. So make sure everything is functional with slides in. Especially when traveling on the road, you will find yourself in places you won't be able to extend them.
Hope this helps.