Is their any rules if I want to use Xpadder for speedrunning Shovel Knight?

Had to google what it was. lol Just maps keyboard buttons and mouse on a controller? No problem there. Have at it.

If you really want to use a Controller over a Keyboard (keyboard master race) this program which i link below is free unlike xpadder and does the same thing.

https://github.com/Ryochan7/antimicro/releases

Joy2Key would also work. Tohloo and I use that for Plague NG+

Mapping automatic mashing or more than one key to one button is NOT ok imo.

Luckily we don't use auto mashing and the game itself allows you to bind anything other than the numbers to more than 1 button.

Certain controllers work fine without j2k. I only use it to bind my spit hotkeys to my controller.