Metal lined....
I have a very old Ernie Hill for my 4" KGPs. Safariland offers serious-use belt holsters that are acceptable for games, AND game-exclusive choices.
Sights are personal, but I prefer the (discontinued) Millett orage-ramp front blade. I use them exclusively on my Rugers.
I've tested some optic-rod fronts, but am staying with the Milletts until someone offers something (exactly) like a Dawson with its recessed .040" rod.
I have used the GPs, and mostly my Redhawks, for Revolver Division in USPSA.