I carry a few weapons IWB for those times when I want to CC. I live in Indiana, and we are able to OC or CC as long as we have the license. I will CC everything from my Karh CM9 to my CZ-75 IWB. For a larger, steel weapon, I have to throw in my lot with the crossbreed style holsters (I use an Old Faithful brand, just what fit my needs). They are comfortable to wear, and make concealing your weapon easy. I have never used the snap-loops, but the metal clips aren't bad once you know where you want them on your pants.
For my Kahr, and sometimes for a Beretta Tomcat, I will use a Galco Softuck, but its just a single j clip. Nothing fancy, but for a small pistol I don't need much.
Now you mentioned your desire for a retention strap. Most IWB holsters I have seen do not use a strap for retention, since the weapon is already a) concealed from prying eyes and b) secured in place by the holster and the belt. When you say you like the "security" of a thumb break better, my question is why? You should not need a thumb-break if your holster/belt are providing adequate retention and yoru attire is providing adequate concealment. I'm not anti-retention-> every OWB holster I use for carry purposes has some form of active retention, mostly in the form of a thumb-break. I just don't see the need for it in an IWB holster.