Important Question on Workflow Animation and Separation before I get into the meat of my game

I have been playing around in UE4 engine for a bit now, however the last 2 months I have spent modeling my character and his ride. I have a few quick questions before I start wrapping up my looping animations.

1st) Should I animate and bring in the Mount and Rider Separately? I’m thinking yes. I can animate them both together however when I do the FBX import I just hide one or the other.

2nd) There’s a mounted weapon is a lance like a turret and mounted off to the side of the well mount. Do I just keep this separate from the mount and attach it in engine to the mount?

3rd) The Rider will have a weapon mounted to the ride that is controlled with his right hand. I want to connect the arm to the mount and move when I move the gun. My problem is how do I make the arm a dummy, yet active when it reaches for other weapons?