Yes, MissionPlanner motor test is your friend. The QuadX8 motor order is very different to ordinary quads, but the motor test order follows normal MissionPlanner behaviour.
Immediately set up the battery monitor and get that working accurately, then go back to the Initial Parameters calculator and redo that to get all the correct battery settings in place, also select “Suggested” settings and accept everything it offers.
Dont deselect the Fence option.
Also set:
BRD_BOOT_DELAY,3000
INS_LOG_BAT_MASK,1
INS_LOG_BAT_OPT,4
LOG_BITMASK,180222
They will be handy for the rest of the tuning process.
I would advise to go through the Methodical Configurator from start to finish.