So this controller for example can be run up to about 28V? I guess then, for efficiency it is better to run at a higher voltage and use a motor with a lower Kv spec? e.g. better to run a 4000Kv motor on 20volts than an 8000Kv motor on 10volts.

I don't know what speed range since the other motor never said! Any idea what is suitable for slow cutting of aluminium and routing wood?