The KPquad not having midi isn’t a big deal, it’s easy to tap/enter the bpm.
Having midi on the KP3 is cool though being able to sequence it, that’s rad.

You can absolutely hook up your octatrack to any kaoss pad and then to the speakers no problem. The level of the KPquad is a little low i’ve noticed, I gain it up a bit on my mixer.

The fun thing with the quad is you can choose multiple effects whenever you want - the KP3 is stuck with a single preset at a time. The presets are very good though, and cover most scenarios you’d want.
If you download the manual and look at the patch list it’ll give you an idea of the combinations of effects it has.

Good luck!