Kodi DSPlayer – DirectShow Player for Windows
Unless I'm seriously mistaken, "Sync playback to display" affects only DVDPlayer. It's "adjust refresh rate" that affects both. In that case you can decide whether to use it for both or only one of them. I personally handle refresh rate switching through madVR only.

Hence, for #2, I think it doesn't matter.
For troubleshooting and bug reporting please make sure you read this first.

Messages In This Thread
Lockup on STOP issue resolved! - by MKANET - 2015-04-11, 21:59
RE: 4G aware patch - by MagikMark - 2015-09-08, 03:27
RE: Kodi DSPlayer – DirectShow Player for Windows - by ashlar - 2015-10-08, 21:39
Alt-F4 no longer quits - by JeffA - 2015-10-31, 20:38