Hi,
The step mode applies to both motors - you cannot have a different mode for each motor. When you change the mode you need to click the update button for both motors to recompute the values.
By design for high speed movements (go-to's and >200x manual slews), the step mode is changed to achieve higher torque. When I was originally designing AstroEQ, I was changing the prescaler for the timers in the firmware when switching step modes. This could only be done by a factor of 8, hence only step modes 8, 16, and 32 could use two different step modes. In the more recent firmware this is no longer the case, I just haven't introduced a way for the 1, 2 and 4 modes to change to a higher mode, and to be honest they don't need to - switching from 1/4 stepping to full stepping wouldn't really gain anything worthwhile in terms of torque.
The go-to rate is trial and error. For the stock motors, start with something like 40x. When EQMOD is loaded by the config utility, try different slew speeds using the NEWS buttons and see what the motors can achieve. Once you have found something they will work at, you can go back to the start and modify the go-to speed to match.
Kind Regards,
Tom.