Hello I've been running 1000x challenge server which has been unexpectedly popular, and every time a player joins the game would freeze. Didn't know what mod caused this, but in F4 show-time-usage I found max value of up to 1 second from map generator. Revealing some chunks on Nauvis using /editor made the lag spike/freeze go away and it's no longer an issue. Tho Nauvis now shows up in /evolution.

So maybe has something to do with player starting on Nauvis and then being immediately teleported to correct planet?

Just realized I never replied to this, yeah I'm guessing it's something to do with that.
Nauvis is hard coded to be the planet players spawn on, and obviously that is contradictory to the entire point of this mod, so I have to clear the surface every time someone spawns in. I don't know why it's so laggy for you, but unfortunately I don't think there's much I can do about it.