I have the bumper plugs on my Ti/Ag. The paint match is excellent.
You do need to enlarge the plate holder holes to install the plugs.
I used a fresh, sharp 1/4-inch drill bit (6.35 mm) and simply turning the bit by hand was easily able to enlarge the existing hole. Again, a sharp bit is best.
I then used a new sharp razor blade to trim bits of plastic shaving from the hole.
The bumper material is very soft and not brittle.
Before installing the plugs it is critical to get the bumper plastic surrounding the hole as flush as possible with the rest of the bumper. When removing the screws from the plate holder the soft plastic tends to deform outward. Even with an enlarged 1/4-inch hole the area around the hole can be raised slightly. The idea is to mate the bumper plug - the back side of which is flat - as flush as possible to the bumper.
Once the hole is prepared, just push the plug straight in. heh heh. Be gentle with the plug - its paint is exactly that - the color is not molded in so the paint can chip and peel off the plastic plug.
Once on the bumper the plug is noticeable, but not nearly as the plate holder holes. (And the whole kit, imo, is much nicer than the ugly plastic plate holder although not as nice as an undrilled bumper.)
get off the phone and drive