This might be better served over in the Roland forum, but quick answer to at least one of your questions…

The way to change a sound in a style is exactly the same way you did it on your G70… Use the Makeup Tools, store it as a User style.

It’s probably been a while since your G70 days, but you’ll find that much is exactly the same, just without the touchscreen, and a few slightly different terms for things like Performance=UPG, Performance List = UPS, etc..

You probably just need to slow down, don’t panic, and soon enough the ‘Roland Way’ will come flooding back to you! 🎹😎🎹