Like DNN Sharp's Action Forms, I suggest having a template for Bootstrap 5 so Live Forms can be styled to more themes out of the box. 

Even on websites that uses a non-Bootstrap theme, I have to go in and heavily modify the Live Forms CSS because it doesn't inherit site styles at all (like buttons or inputs). 

Obviously you might have to account for loading Bootstrap CSS via the theme, vs a toggle in the Live Forms module, but I think it would be worth it.