Is there a way to set up loop points on one individual track while other tracks play thru the sequence?

@ianlary Polyrhythms are done by the micro move effect.
You can do everything with it per track and pattern.

Different tempi per track are not really polyrhythm and euclidian rhythms are a different thing.
Those can be generated with the fill function.

As @paul-8189 said, there is a very popular fr for tracker style loop functions here

and here is another one

You can vote if you like the fr.