#1 In lichess the starting rating is 1500, while in
chess.com is 1200 if i remember correctly. This is why a player with 2000 bullet rating is likely to be a better bullet player than one with the same rating on lichess. For example my blitz rating here is about 2000 while on
chess.com it's 1850. I have no idea about ICC cause i dont play on this platform. About the strength of the players though, i believe that it's preety much the same since most of active internet players play on lots of different sites (at least thats the case with most players i know). About GMs and super GMs though, i think most of them play on ICC, or
chess.com with those special events like "Titled tuesday" or "Death Match".