Driver Level (Catalyst) or Borderless Window Mode, the last is a sure way to force it i think. At least if screen tearing is the thing you want removed.
Microsoft have basically screwed dx8.1 under Windows 10, while dx7 & 9 have no major issues. Enough people will need to complain to MS for them to fix whatever the problem is. It affects virtually every Unreal Engine 2.5 game. As you've noticed - no vsynch and some of the Unreal Engine games will crash on startup, there is a workaround for that, but they remain quite easy to crash if you do the wrong thing - i.e. take screenshots !?!
I've used a variety of converters and wrappers to get most of my dx8 games working with RP but some don't work unfortunately. Yeah, this is why I keep an old W7 pc just in case.
OK. Have you tried running the game(s) in compatibility mode? Also you could try D3DOverrider, I think it should work for DX8 games too. Though for some reason it works worse than RP for me for forcing Vsync/TB but give it a shot.
dgVoodoo 2.5 fixes the vsync issue for games that didn't play nice with dx8 to dx9 converters. http://www.vogons.org/viewtopic.php?f=9&t=34931&hilit=chrome&start=1440#p468698