5G is the one that will drain the battery the most. It’s more high powered than LTE. You could switch back to 3G (much slower than LTE) but I don’t think there would be any benefit in terms of power use since they both share some of the same frequencies.
I personally keep my iPhone on LTE as the 5G where I live has a very weak signal. When 5G is on and dealing with weak signal, it eats battery.