Bullet on phone
Other on desktop
The best device is a physical board
To play with a physical board on chess.com requires that you be a top player in one of their OTB competitions! 😉
Any big device for example an iPad, a desktop, a laptop :0
Imo, touchscreen is best for blitz, if you have a good mouse, desktop/laptop is the best for bullet and desktop/laptop is best for rapid (:
I definitely prefer the browser for other chess.com activities.