Ok, youngster, we'll try to answer your questions.
The AI & TI are pretty easy to setup. Instructions are in English, not re-translated like most products today any you have all of us on the forum to help you when you are unsure, or are ready to get into trouble. Very few people have had questions on assembly, mostly on what the little parts are for.
I never sailed before I bought my first two AI's, as long as you go out is reasonable conditions the first few times, the boat will mostly teach you what it wants, with some friendly (heckling) help here. If you do it wrong, you'll mostly just sit there. When you do it right, you will know it.
The AI's are heavy, but not unreasonably so for car topping. The TI IS HEAVY! On land it's big and heavy, but in the water it's fine. I know of younger, fitter people than I (and probably you) that do car-top it, but most honestly will say it takes a lot out of them, especially after a long sail to do it. Trailering a TI is the best choice. Some on this forum have come up with partial solutions to handling it, if you do choose to do it. (I car-toped on my trucks racks twice, with help, and I hope not to have to again.
Good luck whatever you decide. Both boats are great fun.
You could come visit me on Maui and try both out for a few days.
AI - single -- 350# --- 16' long -- 80# - 120#
TI - double - 600# - 18.5' long - 120# - 200#
- - - - - Hobie Island Sailing since 2006 - - - - - 2011 & 2015 Hobie AIs and a 2012 TI