Pfaff owner here. I ALWAYS use the IDT. My non-IDT feet have gotten very lonely over the past 10 years or so..... I can't tell you when I disengage the IDT and I do quilts and clothes....
As far as STID I use an open toe 9mm foot. I find I have better sight and control and go out of the 'ditch' less. Most of my STID is the only quilting I do, or just add cross stitching if the pattern screams at me :).....