Probably depends on the Unreal Engine. If OML isn’t going for iOS support I doubt they’ll optimize for Windows tablets, so it’s all up to the tablets’ native touch handling. Usually you get proper touch controls as your taps and drags get registered as mouse events. Only thing that’s different is that you’ll probably see the cursor stick around where you tapped.
Drag and drop can be a bit fuzzy unless optimized for touch; and multi-touch is ruled out unless explicitly implemented. That said, I think the game will be fully compatible with Windows tablets’ touch controls. Don’t hold me to it though and don’t go about purchasing a tablet on my responsibility I think someone will double check that during Early Access.