you can devide the total amps by the number of strings you have.
For example, my battery bank at 12v was designed to have 4 parallel strings of 2 series running a 2Kw inverter (1800w cont)
(((So 2Kw*1.15) = 2300 / 12V) = 192A / 4) = 48 A per string now rarely I will ever draw 2 kw hell I rarely go much above a Kw so I can safely divide that 48 by 2 so 24A per string, 8 guage will handle that no issue.
So all my strings are don in 8 gauge, all wiring is exact down to the mm, I use collector boxes so every string used exactly 4 feet to the collector box, the collector box then goes 2 feet to the inverter via 2 gauge, and then from the collector box it goes all so 0/1 gauge to the charge controller and load.
this ensures equal charging and load sharing. No your problem is unless you have all parallel strings ready to rock you got to size it for the battery strings you have now, plus side is your wiring will be way over sized!
So inverter to the main buss 0/4, each battery string to the main buss can be low as 2 gauge with the full compliment of batteries, with out the full compliment of batteries 0/2 will have to be used, and you need to keep all lengths exactly the same
Up to now I have run a full sized coffe pot/ Electric heater, vacuum cleaner, with my inverter and never an issue and no wire heating and all batteries where dead equal last hydrometer test which was yesterday!