You should get a decent amount of reflection off that wall. I have lighter colored walls, and that is how I get by with so little in veg, the bounce off the wall is not too bad....actually measures better than the tent.Cxm 22 3000k 95cri. are luminous. 36v 2100ma I’ve heard good things and can get them cheap. Ok so I can get bye with less than 500w. I’ve heard 50w psqf. But see you guys grow great plants with less. So I’ll just do 4 in each row with a dimmer. No problem with temps or humidity with led. Only got high when I added hps. Concrete wall helps I think. It all needs a paint job.
I would do each row on a dimmer and it's own plug so you can run em individually. Sometimes you get a 3' plant that wants a lotta light and a 5'+ that looks like it burns.
3k is the way to go for flower. Most plants will need a shit ton of Ca/Mg under these lights....start early.