Doubt you’ll get a reply on that, but no, the whitespace is simply never cleared up. I compact containers nightly, using Jim Moyle’s FSLogix shrink script with good success. They don’t recommend it, but you can also create a redirections.xml file to exclude certain directories form being retained in the container. If you run Teams, there are already some required folders that you should add, but are also others that many of us use to keep the size in check.
CPM is still faster in terms of logon speed, but not by much in our environment. With FSL, you want super fast storage - flash, ideally - otherwise you’ll see that slowness creep up. Our logon times are just under 35 seconds in total for a new profile creation, and around 20 seconds for subsequent logons.
You might want to look at Bvckup 2 for replication, as opposed to DFS-R.