> 1400 on lichess is more like 1200 on chess.com, but 1900 is probably 1900.
Not in my experience. I'm rated 1900+ on lichess and 1600+ on chess.com. That's after playing a significant number of games (nearly 500 on chess.com, thousands on lichess).
The way I feel about it, a 1900 player on lichess is an intermediate beginner (like myself), whereas 1900 on chess.com already represents a decent club player level.
For reference, "in real life" (Elo rating / FIDE) I'm rated below 1300 in classical chess, and about 1400 in rapid - although I've played only one rapid tournament, and I don't have a blitz rating at all, which makes comparisons a bit tricky.
For what it's worth though, as far as I can tell, these proportions are about typical.