I have to admit to slowly expanding - or trying to - every year, but by my calculation, I can fit 8 2-3 gallon containers of 32" or shorter tomato varieties under the 4-tube T8 shoplight fixture, especially if in front of my good southeast-facing window to supply the winter
's side/slanting direct sunlight for the lower foliages under the canopy. This winter
, I've also allocated the space directly in front of the window to the Coyote, which is sprawling up and sideways but not so lush as to block the sunlight completely.
As for the peppers, I find that by the time I bring the dug up and grocery-bagged plants inside after letting them go dormant -- leaves shrivel and dry up as the temp in the garage fall below 50's to steady 40's and 30's, then I start bringing them inside when the winter
extreme low (below freezing down to mid-20's or less in the garage) begins in late December-January. If it stays above mid-20's many of them will survive in the grocery bags as long as I give them a bit of water now and then to keep from completely drying out. -- Well, that was a long preamble -- ...Anyway, I pot them up in fresh well draining and enriched potting mix to bring in (including any earthworms I find in the rootball) and the the plants will have lost 2/3 to 3/4 of their root ball mass. I prune off dried up and/or twiggy branches down to leaf joints and branch knobs or just above new leaf buds that are sometimes already starting to peek out, and even the biggest of them really don't need much more than an 8" container until spring.
The smallest dwarf pepper I've grown so far is Peru White Hab, and that one grew pretty well in a 1/2 gal container all last winter
and summer, and many of my overwintering pruned peppers were put in 1/2 gal containers but I think that's kind of small for most peppers to grow in during the summer. At least 1 gallon for the smallest ones, and 2-3 gallon for medium, but I would provide 5 gallon for the 4 footers. (In my garden, they don't get any bigger than that but in the South, you might go even bigger.)
I think 1/2 gal is a bit small even for overwintering the largest pepper varieties especially after they start leafing out.