I am still on my first one that I have owned but not towed as I use to take my parents 14 footer out. While mine is only 20 it is what I could afford and what my TV would handle at the time. If you have the means to get the right TT first I say do it. There is no harm in driving a little slow either to be on the safe side. We usually leave a little before some of our friends as they like to haul but at 75-80 while I don't mind the 55-6 ish (if I stay below 60 I get better MPG). My advice is spend some time in the TT you want and make sure you have room for everything or a place to put things like toys for the kids, the dog create ect. Think about dishes pots and pans ect. as well as all the things that you think you will need and then add a few you don't because they will end up in there any way.
Just for consideration if you are not using camp grounds and are going boon docking larger places are usually not tree covered. You know the area where you go better then most.
Welcome and Happy Camping