It depends upon what I’m wearing and if I’m doing the “smooth front” as you mentioned.
I find the gaffs are not enough alone. A gaff is usually to help keep your tuck, “tucked”…
The gaff is usually a robust undergarment that will keep your stuff where you put it.
I find that tucking isn’t the most comfortable thing to do…but it’s a necessity.
Forgive me if I get this wrong, but it sounds like you haven’t really practiced tucking.
Pushing the testies up into the inguinal canals, pulling the penis back toward the rear, and then keeping it there while you shimmy your gaff up into place… I’ve never needed tape with a gaff to hold my tuck.
Conversely, I’ve never done a tape tuck… I always just used a gaff. It’s a personal preference really…
There are videos out there that can walk you through the steps…