I have a split panel set up. 3.8kW facing NW, and 5.2kW facing SE. 9kW panels in total.
For the purposes of the Settings / Solar Capacity figure, I put 7.5kW as the array size. This seems to work fine, and not particularly influence anything in WW negatively.
From my experience, I would suggest it's more important you get the Advanced / Battery rate, and Advanced / Inverter rate correct, and I re-jigged mine slightly to improve WWs calculations for how long to export/charge for to reduce/add x% SOC.