1. play all the games you want.
2. yes, but don't buy 3rd party ones, they break to fast.
3. i recommend official ones only and if you need to replace the internal joystick by soldering or have someone whom knows how, get these: https://www.amazon.com/gp/product/B09LVPD565/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 to replace the wii u pro controller ones.

you still need the gamepad for navigate in most games.

you could get the wii u pro controller, but if the thumbstick isn't responding like it should - you might need to buy 3rd party internal thumbsticks like this: https://www.amazon.com/gp/product/B09LVPD565/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 got to soldering them in and do a little clipping on the stick part, since it was made for ps5 controller.

those thumbstick been working great for me like 3 months ago and still feels like new.