No experience yet but the G19 in my avatar is mine and has the RTF2. I have heard some of the some reports that you have about the RTF2 causing clothing/wear issues for LEO's. Supposedly, feedback from LEO's is what caused Glock to come up with a different "RTF" for the Gen4 guns.
I just applied for my CHL this morning and am awaiting a holster for my 19. Being left-handed definitely makes it harder to find holsters in stock, be it at the range store or online. But hopefully I'll have a holster soon and can start giving you some feedback.
Another option to provide some relief for your own skin when carrying IWB might be a holster that has some leather or other material between the grip and your side. Right now, an example escapes my memory but there are some companies offering holsters that put a shield between the gun's grip and your side. That might help to partially alleviate some of the rubbing issues that you are worried about.