During 12/12 lights, how far should I keep my LED&...

Hello my friend It really depends on how large the plants are and what strain. After you grow several strains for a while you'll find that they have vastly different light tolerances. Sativa dominant plants are hard to burn but some indica plants don't like the light very close at all.  I would start seedings or small plants about 3 feet from those high output leds you have. If they can tolerate it work the light down slowly to about 18". There's really no need to run closer then that in veg. In flower if the plant can take it you can go down as low as 12-14". That is really strain dependent. 18"-24 is safe. 👍That's a good rule of thumb with these lights. I don't think you'll get too much stretch at those lengths and you'll get good growth without stress.  Watch for the leaves doing this. If you see this condition move the lights up a few inches.  Part of becoming a good grower is learning the language of the plant. This is the plant telling you to back the light off. The leaves will tell you many other things if you learn to listen. =) May the force be with you 💪 Good luck for your grow 🌱

Some reviews showed that a height between 18" to 24" from the top of the plants to the LED should be fine if fired up to about 120W per QB96. For that early vegetative stage even thats way too much, but I know you know you will dim them down to about 30W per Light.