OK, here's what I have learned so far:
I purchased the above described hardware. Installation of the Sapphire Radeon R9 Fury 4GB HBM card went without issue and I used it with my old monitor setup for several days (while waiting for the FreeSync monitor to ship) with no issue.
My Samsung U32E850R arrived yesterday. In short, it is Beautiful!
Attempting to update to latest released AMD drivers (revision 15.7.1, released 7/28/2015 for Windows 10 x64) was problematic. Could not get the driver to install happily (yellow triangle exclamation icon in Device Manager) and Catalyst complained that no Radeon drivers were found.
Updating to beta AMD drivers (revision 15.9 Beta, released 9/27/2015 for Windows 10 x64) went smoothly.
The Samsung Monitor has 3 FreeSync settings, Off, Standard-Engine and Ultimate-Engine:
With FreeSync: Off, things are as normal.
With FreeSync:Ultimate-Engine (adaptive refresh range of 40-60 Hz), computer will NOT detect/use the non-FreeSync monitors AT ALL. If they were in use at the time I changed the FreeSync setting in the monitor OSD, they went blank. Windows will not subsequently detect them. AMD Catalyst will, at this point, add an entry to My Digital Flat Panels | Properties to enable FreeSync.
With FreeSync:Standard-Engine (adaptive refresh range of 50-60 Hz). , computer will detect/use the non-FreeSync monitors. AMD Catalyst will add an entry to My Digital Flat Panels | Properties (for the FreeSync monitor) to enable FreeSync. Windows detects/uses the non-FreeSync monitors. When I fire up a game (Fallout New Vegas) the game goes full-screen on the FreeSync monitor. The non-FreeSync monitors stay on and usable.
I don't have any report at this time as to the goodness of FreeSync. I don't tend to play twitchy games (e.g. FPS). I can say that playing Fallout New Vegas with this hardware setup, Resolution at 4K, Detail on Ultra, AA on 2 Samples, is beautiful!
Hope this is useful!
Doug