One more thing: Not all LED's with the same part number have the same performance. There is normal variation within lots, and even more lot-to-lot. That's why many LED's can be purchased pre-binned, where their luminosity has been ranked so you can buy the same dash number and get tighter matching between otherwise "identical" part numbers.
Without such selection, done either at the manufacturer or by you, a string of "identical" LED's, whether in series or parallel or a combination, can yield very noticeable brightness differences. As standalone parts this is less critical, but in an array of LED's it can be anything from "don't care" to "what a piece of junk".
This isn't strictly related to your original question, but since you're talking about arrays and drivers it could come up as you play with various options so now you're prepared if/when you see an unexplained brightness variation.