I was wanting to get into speedrunning this game, and I'm kinda stuck on the Nintendo Switch version for now. Therefore, button-mashing isn't easy. Is there a "best way" to mash on Nintendo Switch? Or is it better for me to switch to PC version?

Thanks

It's generally better to move to the PC version, but if you insist on using switch, remember that when docked you can plug a keyboard into the USB slot.

what you can do for the switch is, if you have a dock (which you should if it's a standard switch) you can attach a (non RGB) keyboard to the dock. It won't do anything in the main menu of the switch, but as soon as you're in the game you can use the keyboard as the controller :)