I have about 8 or 10 Blade-Tech holsters, mostly IWB and OWB Belt Loop, but have tried the Tek-Lok, Stingray, Paddle and MOB/SOB also. I still have the first IWB that I got so long ago I don't remember (maybe 12 years or so?).
The IWB will be the most concealable by far. My favorite holster. Or maybe second favorite after my Mika and Safariland pocket holsters, because I carry a J just about any time I am not at work. The next one I get will be the Nano IWB, as that looks even better.
The most concealable OWB by Blade-Tech is was the standard belt loop model where the belt loops were one piece with the holster body. It was extraordinarily strong, rode the closest to the body, and didn't rock or tilt as the paddle does (on me). They no longer list that model OWB on their website.
The Tek-Lok, Sting Ray and Paddle allow them to produce one holster body and attach any of the belt attachments. It also allows cant adjustments at any time. All 3 types stick farther out from your body, and are relatively less concealable. The paddle is too curved for my fatness, and so the front and back edges dig in uncomfortably.
If I was buying a B-T OWB now I would try the Eclipse.
Have I mentioned how concealable their IWB is?