String Selection in Multiple orientation with Multiple MMP Input

[engr.mohsin6]

I want to design a solar system (15.48 KW =36 Modules x 430 w per module) on two roof (28 panels on one roof and 8 on other) having tilt angle of 30 and 20 degree respectively at location of 41°18'06.0"N 0°59'17.8"E. I selected Pv module of 430 W and a hybrid inverter (8KW) of Fronius_Symo_Gen24_8_0_Plus.OND (Fronius International) having 2 MMPT inputs. 
During Design, I configured 18 module in series for 1 inverters and the same for other. Each inverter have 2 MPPT so i have following confusions. 
1. Do i need to configure 4 strings (each of 9 module in series) with 1 string for each MPPT or to connect 18 module with one mppt? (Please review snap)
2. Location is Northern hemisphere, so panel should be faced towards south having azimuth angle of 180 degree. But when i select 180 degree, Loss due to Optimum goes upto 42% (snap attached) while it comes 10% when azimuth angle of 0 degree. Why it is happening? 
3. What will be azimuth angle in my configuration ?
4. What can be the best configurations ( No of strings and MPPT inverter)?
Valuable Expert opinion and prompt response will be highly appreciated, please.. 
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