I have a Juiced CCX but I see no reason the RCS would be any different. The RCS Bottom Bracket(i.e. fatbike standard) is wider but that shouldnt affect the crankarm.
No, the crank/crankarm on the RCS/CCX is not ebike specific.
Yes, you can replace just the left crankarm. Just need to make sure you get the length and offset correct.
You might also want to make sure that the square taper hole on the crankarm relative to the arm is the same. I have never had an issue with this but have heard of some people having issue when replacing just the left crankarm.