Blitz - best for trying out new openings. You get a lot of games in a shorter period of time, so you can get a quicker feel for openings you are trying out. This is also the time format most titled players use on chess.com
Bullet - don’t play bullet. Only thing it’s useful for ur training you for time scrambles at the end of games in longer time formats. It’s chaotic, and you will not play good chess here.
What are the pros and cons of playing each of these modes and which of them is the best in your opinion?