I’m going to operate under the idea that you understand the basic voltage needs and such, so i wont go into detail on that.
Max thrust is based on your motors, unless your under powered voltage wise. As for flight time, it depends on what your building for.
If you want a small, fast, nimble drone, a smaller batter is less weight, but in the same line, there is less flight time. But if your building a camera drone, one to fly slowly and enjoy the view, with less need for speed, a bigger battery would provide more flight time.
As for Transmitters and such, its all budget and personal choice. I have an 8 channel Devo 7, and i love it, but my next one will be a 10 channel Futaba. If you have any other questions, ask away.