Bulk will do an initial replication which uses HBR under the hood. Once the initial synchronisation has occurred it will maintain a 2 hour RPO on that sync. When you initiate the migration switchover, HCX will power off the VM and then it will do a final cold synchronisation prior to cutover.
Stats wise you can follow the following KB:
Use this to get all VMs and map the VM ID to the one being replicated:
Then use this against the vmid of the VM you are interested in to see stats.
vim-cmd hbrsvc/vmreplica.getState vmid