Consider the following scenario:
ATP treats each SEPM as an individual identity, hence we always enable the option 'Replication is enabled between all SEPM's.', when adding replicating SEPM databases.
In above situation, as a best practice we either can keep Replication sites or standalone site. Or uncheck the replication option and configure as follows:
Note: Please make sure the number of SEP clients as per Sizing guidelines.