The tuckable holsters do a good job of concealing a G26. I have a CompTac Minotaur and you can settle the pistol very deep if that is the way you want to carry it. I typically pull out my shirt tail a little so it will be loose enough to conceal the butt of the pistol. Even a golf shirt will conceal it. But you will always have the belt clip or loop or belt straps showing.
Side note: I don't often wear this style of holster due to how difficult it is to put on. My work took me to lots of places that I can't carry and lots that I can. Particularly schools. So I was constantly taking it on and off. Easy enough with a simple kydex holster with belt clip, but the tuckables are much more difficult to get into proper place. Nowadays, I dress much more casual and typically wear my shirt tail out. So it doesn't matter. I often carry a G22 now.