I put swivels up about 18'' so it doesn't effect way jig it tied on and hangs. Small Barrel swivels can be pulled up through the rod eyes if need be. I have fished with bigger Tube jigs for years and seen lots of folks get upset with line twist. A simple barrel swivel will take care of it most times.
On the other question , a clear leader can't hurt when using hi-vis even though some folks say it does'nt matter. I never liked hi-vis my self.