1) They are useful only for attaching a line on the body of a tarp. There are better ways to attach on the sides. For a plastic tarp, simple sheet bends work fine on the corners and give a stronger, less distorting attachment.
2) There are simpler, lighter ways to attach a line on the body. 1" styrofoam balls pinched in the fabric and looped with 2 half hitches or a figure-8 noose will be lighter.
3) All these devices - Grip Clips and their clones as well as balls and line - tend to be hard on the fabric. Repeated use will breach any fabric except maybe 4mil poly. Tyvek and silnylon and even light polyurethane coated nylon will develop some leakage after a while because of the concentrated stress and abrasion.
4) There is little reason for "quick assembling and modifying tarps." If you have corner pull-out points and one or two on each side and a couple or 4 pulls on the body, you have more than most folks ever need. Furthermore, permanent pull-outs are faster to use than any detachable device. And you don't have to keep track of extra parts.