Depends on your level of comfort with over paneling. Most people try to stick with what each SCC gives in their manual. You have to always keep in mind that panels do not push watts. Loads pull watts. You SCC loads the panels based on its rated charge amperage (if loads to it like the battery are available). Watts = Volts X AmpsI've been looking at four models of inverters and their manuals but only one states that the PV array can handle 27A, the others don't. At least not that I can see. Is there a way to determine how many strings you can use on one inverter?
In regards to which panels to buy. Make sure that you price in shipping costs. Often for pallet sales the shipping cost can make what seems like a good price per watt be a bad price. That and you might have to buy more panels than you want or need in order to get the pallet price.