When applying loop effects on the Play in Performance mode, for now it doesn’t matter what tracks you choose - it just loops them all.
According to the Polyend Play manual:
In the case of most of the punch-in effects, only the selected tracks will be affected. If no track is selected then changes will not be audible. The exceptions are the eight Reverb preset, and all the Loop effects.
If the Play Plus processor can handle this, it could make a difference.
Flexible ways to loop tracks.
Declined wish for the original Play:
A wish to make loops in a different way: