A GM has an elo of at least 2500, and Magnus Carlsen has an elo of almost 2900, so I think you can safely say that most games between grandmasters at a level of 2400-3000 elo. This is obviously very vague, so I think you can best describe it as: Most of the games among GM's are at a level similar to 2 chess computers, with an elo rating of 2500-3000, playing against eachother.
If you take this description into consideration, how high would the level of games be at a blitz and at a bullet tournament for grandmasters? Would they be significantly lower (like for example 2000-2400), or would a good grandmaster like Magnus Carlsen still play at a level around 2700-2800?