Speaking from experience... I have had 4 disserent truck campers, 2 different trucks. Launced boats, pulled enclosed trailers, boondocked, hooked up at full hookups. From a pretty basic one to a dry bath with gen, sat and HDTV, plus mega solar power.
Really a neat way of RV-ing, but mainly for short term. Longest time we spent in ours was 2 weeks. Could have easily gone longer, but I wouldn't want to spnd a summer in Yellowstone in one. Too confining.
As to tanks, yeah, for boondocking, you need to do things a little different. strict budget on water etc. However, we were usually within an area we could dump and replenish.
If I had unlimited time, money and space and only 2 choices in RV's One would be a TC. Also a great choice for an AK trip.