Since updating to 1.16 we have got chronic lag when players generate new chunks. Only minor changes to the command system (to account for checking the dimension a player is in)
No change to the server host. We have 6G Ram - we were fine with up to about 10 players on 1.15. Now it can barely manage 4 or 5. It has been very close to unplayable.
Please check if setting sync-chunk-writes to "false" in the server.properties improves the performance.