Our first TT is in the first layout below - 21.5' overall, 5K GVWR. We thought it was our "forever" trailer. Had it at an independent RV shop to buy some parts and the owner said it would not be our last trailer which made me feel a little bummed out and confused. Towed this TT with an F150 with 4.6L V6 which was seriously under-powered.
Our "forever" TT lasted only one year before we realized it was way too small and uncomfortable. We had to squeeze tightly by each other when passing between the kitchen and bathroom. Having to watch TV from the bed or from the dinette seating was very uncomfortable. Lack of a sofa turned out to be a big negative. Insufficient interior storage. Small bathroom and tub/shower also a big negative. We lost around $4K - $5K when we sold it which included a lot of mods I did but at least my BIL has it and got a very nice TT at a low cost.
Ended up with a 29' TT shown in the 2nd floor plan (6800 lb GVWR). Now on 3rd season with it and totally love it. Large walk-in shower, sofa, lots of interior storage and above-average kitchen counter space are all HUGE pluses. Have been to several RV shows since purchasing it and have not seen anything that we'd want to upgrade to even if we got it for free. In the process of upgrading to a longer TT, we also upgraded to an F250 which has also turned out to be an excellent move.
If you have no experience with a TT, I would suggest buying a used "starter" trailer to see how it works for you before losing a lot of $$ on something that you regret afterwards. Or rent one somewhere for a few days. There are many things you won't learn about until actually owning a TT.
Good luck and have lots of fun with whatever you get.