System.mdw - sometimes need to replace if service isn't restarting. Check event log, if no obvious reason for service not restarting (usually straight up tells you if it's a license issue or similar) then can replace. Keeps the Sync logins though, so any non-default logins or changes to default login will be lost.
KS_Inbox - keeps old inbound emails. Might need to be replaced with default copy if the migration tool gets stuck reading the Access DB.
KS_Object - In SQL this includes the KS_Changed and KS_Triggered Access DBs as well as KS_Object.
