You will typically want to set the driver's current limit to be at or below the current rating of your stepper motor. One way to set the current limit is to put the driver into full-step mode and to measure the current running through a single motor coil without clocking the STEP input. The measured current will be 0.7 times the current limit (since both coils are always on and limited to approximately 70% of the current limit setting in full-step mode).
One remark: the logic power supply from Arduino to RESET/SLEEP is actually not needed to adjust the current limit.
So I wouldn't mind if you take your first picture - my reply was jsut a technical remark. For practical purposes your set up is very well done.
The above mentioned formulas are only valid if the breakout boards come with the specified sense resistors; e.g. for DRV8825 these resistors come with 0.1 Ohms (per coil).