I have an upper roof and lower roof (tilt angle is zero) - (Flat roofs). So, I believe single Sub-array with "mixed orientation 1 and 2" for each roof would be suitable.
Also, I am planning to have either (one inverter per each orientation, so total no. of inverters would be four (two for the upper roof and two for the lower roof)), or (one inverter for each roof with 2 MPPT).
What do you think for the above design strategy?