1/384 microtiming is enough.
If you want to use timestrech and increase pitch at +12 for shimmer fx, you need to increase microtiming up to 7/384 at 120 bpm.
For recording length, it has to correspond to time between trigs. You can use several rec trigs and trigs, to refresh recording while using pitch fx. You can always lower pitch. Once recorded you can use reverse, +12 pitch without timestretch…
For full reverse you need 2 recorders IIRC.
