DFS Locks

If Win2008+ DFS Replication tries to replicate open files and 16 of them are locked at once, would DFSR cease to replicate any further until at least one unlocked?

No, those files are skipped and retried. DFSR will retry after one second, two seconds, four seconds, up to twelve times with a maximum timeout of 5 minutes between each retry. DFSR will then stop retrying that file for 10 minutes and re-enter the same retry cycle infinitely. The DFSR events are throttled and the events doesn’t match the actual number of retries.

Locked files definitely have a negative effect – all these retries aren’t free – but you will not completely block behind 16 files through bad luck.