There are advantages to looking for the truck and considering what trailer at the same time. You don't want to make the substantial investment in the truck, then discover that it's not enough truck to tow the trailer you want. You either have to upgrade the truck (at a substantial cost), or settle for a trailer that's less than what you really wanted (which costs you in regret later).
In our case, when I bought the truck, I went with a 2014 Ram 3500 cc/drw/lb with the CTD and Aisin transmission. It meant that when I drove up to an RV dealership, I could tow anything on their lot. I wasn't limited by the truck. I was free to look for the RV model and company that best suited our needs.
Some folks get intimidated by the size when they think about driving/parking a truck like that. After a week or two, it's second nature. I lived near the strip in Las Vegas at the time, and never had too much difficulty in parking or maneuvering. While parking garages are mostly too small/narrow, there is plenty of surface parking available. The one thing you learn is that you may have to pull through two parking spaces and walk a little more, but it's good exercise. Even when the baby was due, my wife didn't mind a little walking.
A trailer the size of these takes a little care when towing, but not much more than a smaller trailer. Backing it into the first place we parked wasn't a lot of fun, but the space was designed for something a little shorter. We made it in fine in the end. Once you practice a little, it too becomes second nature.
My recommendation is to get the most truck you can. Then you can get whatever trailer you want.
