I take them off as they get in the way and sit closer to the centre of gravity anyway, so shouldnt make a difference even if they were slightly out.
I also take them out sprocket and cush should be close enough to be balanced some people dont balance rears i talk to . I always do for peace of mind
never on but depents on your balancing way (mean if you have an auto balacing macine that spins the wheel or not) couse if you have the balancing machine you need to remove the sprocket so you can tie the wheel on it