Oh I missed half the question, getting late!
So they are currently available in qb 120, 288, and 304. The 120 is like a 65 watt max board, not good for this application. If you wanted to do a veg light for your 2x2 it would be a good choice though. Or maybe 4 of them in your 3x3. I’ll hsve to look at that, but probably a little more diy involved to make it work good.
The 288 and 304 are pretty much the same as far as available output. The 304 has one extra string of diodes, but it also has higher operating voltage (104 volts nominal I think) which makes driver configuration a little more difficult. The 288 is like 54 volts nominal, so there’s a butt load of different drivers available.
Personally, I like the 288 for the operating voltage. But I also get bored with stuff easily, and do a lot of moving stuff around. If I bought one 304, and wanted to add two more later, you’re limited to parallel wiring because the connectors are only rated for 300 volts. And there’s only a couple of drivers that will even do it in parallel. The 288 on the other hand, no problem at all.
If there’s any chance at all of you becoming an led nerd, get the 288. If you think you’ll build it and leave it alone for 50,000 hours it doesn’t make a damn bit of difference lol.