I am planning to start the challenge on the Switch version. There is no key configuration option in Game Boy Nintendo Switch Online, but the controller can be key configured through the Switch's own console settings. This makes it easier to switch between morph ball actions and missiles by assigning down and select button inputs to different buttons, but would such a setup be allowed in the Switch version of the challenge?

As long as there is only one button for each input I don't think it would be a problem to find a comfortable configuration as emulator can do so already.

Thanks for your reply. I will continue to practice in that style for now.