Hi Goddo!
First and foremost, welcome to the Ori community! We actually have a discord server, so please add me on there (trojandude#9178) and I can PM you a Discord server invite.
Secondly, double bashing is actually really hard to achieve on Controller as you are required to hit the one frame window in order for it to work. The good news is that the updated route actually doesn't require any double bashes to be competitive. We have several controller runners that use a regular bash setup for Sorrow Bash, and you definitely don't need it for any other section.
As far as remapping, you are definitely allowed to remap items using Joy2Key, Big Picture, etc. This is generally done using the right analog stick, but you can do whatever is comfortable to you. This includes Toggling UI, Rocket Jumping, Cdash+bash, etc
I hope this helps and please join the server, and never hesitate to ask questions there! We are always here to provide advice on the game and speedrun :)
-Trojandude12