Is it possible to restrict the Active Directory requester import to a specific OU?

Is the recommended way to do this using the LDAP sync rather than AD Sync?

If so, what effect will the be on existing requester and technicians if I swap from AD to LDAP sync? Will the new LDAP sync simply take over the existing users from the AD sync?

The purpose behind this is that when user accounts are disabled they are moved to a specific OU for a length of time. If they are removed from SDP they are re-imported when the next sync runs. We also have a bunch of service accounts, contrator accounts and administrator accounts that do not need to be imported into SDP.