I was some 1800 here. But took a 10 year vacation. Restarted on lichess and progressed to levels higher than I think I ever was.
At lichess my bullet is 1300 blitz 1450 and rapid 1550
Correspondence at 2050.
When I came back to chess.com 1200 players moped the floor with me on bullet and blitz and I was dropped to 700 bullet 1000 blitz and 1300 rapid. Correspondence at 1350.
Well the main issue with check.com when playing bullet is higher latency time so I run out of clock fast and many games are dropped.
Also. I'm not that good and a bit old to play blitz even rapid, but still can't figure out why my correspondence rating is much lower than lichess
If chess.com is more laggy than it is more laggy to your opponents as well, not just to you. I doubt lag has an impact on your rating.
I played chess.com 24 hour games. On lichess I play 30-20 live games. My ratings are very close.
They both use Glickman ( Glicko)rating system. The longer you play on both platforms with same frequency, I would expect the gap tighten.