Those optimisers seem to mostly intended to correct for poorly designed systems. Mismatched panels, different panel angles etc. Considering that you can buy solar panels for around $1 per watt output. Instead of spending $1500 on optimisers, get an extra 1.5KW of panels instead.
And since you will have the panels facing in 3 different directions. The panels will never all output peak power at the same time. So you can actually connect slightly more panels than the inverters rated output power if you want. But still important that you group the panels based on which direction they point. (eg NW facing panels to MPPT input A, N facing panels to MPPT input B, NE facing panels to MPPT input C)