I have tried and used many over the years in various cars.

BY FAR the most comfortable to use (by design of the shoulder buckle) are ones from LUKE.

They have a flatter back and more rounded buckle so sit comfier on the body when pulled tight.

The bottom 2 (or 1)strap(s) can go back to the same place yes.

*EDIT* By same place I mean its own mounting point under the seat