I've created for test two sites by ADSS.
Sites1 with subnet 192.168.12.0/24 and
sites2 with subnet 192.168.11.0/24
both are connected via VPN.
Each site has only 1 DC.
Also I created IP_LINK between sites with replication sheduler (replicate every 18 minute).
When I create user, group, change user attributes and other - replication between DC proceed immediately not by existing sheduler.