On iOS 10, it does not disable animations but replaces them with fade-ins/fade-outs. I don't know the behaviour on iOS 11, but I suspect it is going to be the same.
It is, but it does feel a bit speedier. Interestingly I’ve had Reduce Motions on for quite some time and just turned it off. Feels kinda newish now, but I guess I sometimes just like change for changes sake.