When replicating information between sites Active Directory will designate a server in each site to act as a gatekeeper in managing site-to-site replication?

Answer 1

if you have not selected any DC as bridgehead server then it automatically follows ISTG - InterSite Topology Generator,chooses its own DC to replicate and if this link is down makes another but if you define bridgehead server,in that case if the link fails the replication stops.