The problem with an original side trim kit, as linked, is that on most replicas the door handles bare further forward. The front and rear spear fit fine. The door spear needs shortened, and you need an extra piece to cut a custom small piece behind the door handle. So... you need a full kit, plus 1 extra piece. I can't say that ALL cars are like this, but I have added enough these kits to several manufacturers cars and they have all been the same in my experience.
As for clips, the metal clips can be used in some places but not all. the plastic VW side trim clips work just as well and do not require getting to them from the back side, so you can put them anywhere.
Finally, if you do decide to go with this nicer kit, there pieces are MUCH stiffer than the VW side trim most builders use, so you have to shape the pieces to the body before attaching them. The VW stuff will clip in place and stay, but the restoration stuff has enough spring back that it will pull away from he body if it isn;t shaped to fit.
Hope that helps.