I have a room attached to the garage that I used to use in the same exact way! I loved that room!!! Now it is an off the grid room, and so far pretty useless. I did move some exercise equipment in there, so that is good. But we had to get a couple small greenhouses for our plants over the winter and to have starters in early February.I don't have the greenhouse built yet. We have an add on room for a sun room that has its on AC and Heating system. We use it for plants and did use it for brooding chicks. Now we also use it for kennels for taking care of hurt or ill birds. These two lights will illuminate a half sheet of plywood topped table the long way. All we need for starting plants as they go from tray to the garden. At least most of them will.
I don't have a big garden area. We have raised beds and they are fenced off, but the total planting space is only 256 SF so I have to be prudent in what I plant.