cable sizing is all about wire resistance and the amps involved...
wire resistance is a combination of the wire diameter(how much copper), AND the distance involved.
using a pencil and paper layout your measurements...remember that when adding up wire distances its the complete wire path that counts.
for example, two devices 10ft apart connected with wire means you have 20ft of wire.
once you have the wire distances, use an online calculator to get an idea of the minimum wire guage you should consider.
When working out the maximum current draw, I use the surge limit of the inverter, not the "nominal" wattage.
This link here will get you this
minimum wire guage number (fyi, I always use a 1% allowable voltage drop)
NOW, this is in important step...if you think you may need to increase you panels, move them further away, or have a larger load "someday", use the calculator and play around more amps or longer cable lengths.
It is always nice if you decide you need a few more panels becuase there are more slightly cloudy days than you planned for you can just attach them without having to worry about wire.