The best way to improve is to play slow live games (2 hours+) followed by review. However if you only play under ideal conditions, then you won’t get enough game experience. So I play mainly medium-speed internet games (~45 minutes) generally on other servers, and 5-30 correspondence games at a time on OGS.
Advantages of correspondence games:
- Fewer blunders.
- More time to explore complicated positions.
- More time to count endgame values.
- Even if you don’t have time for live games, at least you can play a few moves a day.
Disadvantages:
- Can be a burden if you have too many games at a time.
- Delayed feedback between your mistake, and punishment by the opponent and/or AI review.
I don’t think visual memory is a factor here. I did very poorly in memory tests a few years ago
https://forums.online-go.com/t/visual-memory-correlation-with-go/
and am not much worse at live games than at correspondence (was 1k after the 2024 “blitz” WSC, now back to 1d after 34 games, mostly correspondence).