It all depends on your size.
When I was young and doing manual labor, I could carry a full sized 45 goverment model in an inside the belt holster and then just leave my shirt untucked.
My brother has a tiny 380 and a holster that looks like a wallet. I would be concerned about how quickly I could get to the weapon and effectiveness of the round, but it sure doesn’t look like he is carrying.
I hope the wallet-holster is legal.
Bianchi made a bunch that were declared AOW’s, (Any Other Weapon) which made them legal to own only with a $5 NFA transfer tax and registration.
Goofy, I know...but still, to carry those particular holsters means you are actually committing a felony and can be arrested on the spot.
Ed