These will be the changes for server in the update:-
1. Nether will be reset and new 1.16.1 nether will be generated. So if any player have base in nether they should move valueable items from it.
2. Vaults plugins we were using is no longer supported in 1.16.1, so everyone must remove their items from vaults and save it.
There will be new vaults plugin in 1.16 /pv
3. Linkedchest/big chest: this plugin also not supported and we don't know how long it will take for it get updated. So remove these chests if you have any.