Personal opinion – I’d buy the base truck (4×4/SRW) and add the camper. The truck is where the big investment is to begin with. If you decide, like we did, that you bought the wrong camper, then it’s a lot less money to trade up/down.
I’d start on the small side on the camper. Yes, you can plunk the Taj Mahal on the back of your truck and go lumbering over hill and dale, but smaller is (usually) lighter, less expensive and more maneuverable. Besides, you might decide that smaller rig is not bad at all. We ended up going to a smaller camper and love the backcountry agility it provides.
You didn’t mention if you are solo or a couple. If a couple, make sure to involve the SO! We looked long and hard at the pop-up campers and while there’s a lot to like, we decided a hard side was more our speed. My wife is **really** not a fan of the cartridge toilets and my back ain’t that happy with them either.
All this is me talking outta my bellybutton – I’m sure you’ll get other opinions!