Thanks, that is helpful. After posting this I notice there's also a smoothie forum here.
The MKS sbase is not really open hardware but seems to be copied from a number of different Chinese manufacturers. The genuine Smoothieboard seems to have a more robust driver design in the electronics.
I built a 1000x1500mm OX CNC and using the same motors (NEMA23 178oz/in) on all. I'm also running at 24V. We'll see how that goes. Your current settings sound reasonable and I think I should be able to go with 1.7A all around.