I know IORoot works on KitKat, wondering if I should accept the OTA or root my phone now (its stock on 12B) and install the 2GB leaked OTA (which is 100% identical) with a custom recovery. That way I can also install some of the custom roms on XDA.
The choice is completely yours as IORoot works with KitKat so there really isn't a problem. As for installing the 2GB leaked OTA with custom recovery, I'm guessing you're talking about the infamous loki exploit? It does work fine and if you run into any trouble well there are guides to get out of that (INSTALLING TWRP on LGG2 (VZW, AT&T, TMobile, KT, d802, others (look it up on google by typing XDA with the title)). So go ahead