Mac - Output different audio streams to two separate devices

Solution 1:

I wrote all this before realising you want two routings from one app - that's not going to be possible. I'll leave this here for future searchers.

There are only two apps I know can do this, both by the same company, Rogue Amoeba.

The cheaper & simpler one is SoundSource - $35. There is a more complex/expensive one which can also record any sound source to disk as well, called Audio Hijack - $70.

SoundSource can do all you asked & more.

There is a late third - Boom2 & the newer Boom3D - but it's a notorious crasher & speaker destroyer unless you switch off everything except the routing [judging by the many questions we've seen in here about it. I've never tried it personally].