I have a FWC Hawk shell, with a front dinette. It has a N/S king size bed, there is a ton of storage in the dinette plus I added two DIY cabinets for clothes and food. The dinette converts to a single E/W bed, 6ft long which allows sleeping with top down for one person.
I've been a full-time RVer for more than 22 years, but not in my truck camper, I live in a motorhome and tow the F150/FWC behind it. I love camping in my FWC and have taken trips up to 6 weeks in it, did a 3 month trip in another skamper pop-up truck camper in 1995. I know people do full-time in small truck campers, I just don't know how they do it long term. Living is different than camping. So if you are planning to travel and camp for a year or so, I think with good planning one of the truck campers mentioned will work. If you are truly planning to give up the sticks and brick life style and live full-time on the road, you may want something a little larger. I think a well appointed camper van might be a better way to go, if you want to stay small.
Any way, just my two cents, Good luck