I've had my Shield 3.1" (1st gen) for several years now, keep on telling myself "I really should start carrying that thing". Analysis Paralysis has prevented me from buying a holster that I think would work.
During the workweek, I'm in Carharts and a tucked t-shirt, overshirt/hoodie when it's chilly. I've never really been an "untucked" sort of guy, but around the house I could learn to live with it. I dress formally for church, but it's often with a sport coat/blazer or vest. OWB would work in those cases.

Do either of the aforementioned holsters actually allow for decent concealment and tucking in of shirts? I've looked at the Enigma, but that seems to be rather involved for day-to-day wear. Belly bands could work, if I found one that didn't look/feel like some generic "universal fit" rig.

5'8", somewhat stocky at 175 lbs, very slight belly (working on reducing that)

Lighttuck FTW, couldn't be happier.
Doesn't exactly look it, but it's very comfortable and conceals very well with just an untucked t shirt.

With most IWB holsters, it's best to go untucked.
IMO, IWB holsters for tucked in shirts aren't a wise solution.  Bellyband, pocket, or ankle carry are likely better options in said scenario.

t-shirt tucked in? Would you know of any photos that shows what it looks like while carrying?

I have Vedder for all my handguns.

If you can hang on for a bit, I'll take photos of all the IWB/OWB profiles tomorrow.

Glock 19
M18
P365
1911