The JBJ nano stock lights are enough to keep most softies and some LPS
. Depending on the light requirements you may not see the best color out of them though. I had a 12gallon JBJ that i kept all sorts of things in with good success. The nice part about those tank is they are pretty shallow so they light they have stock does well.
My brother just did a build on the same 12 gallon i had that i gave him where he put DIY high powered LEDs in there. They have so much light that he has to turn them down so it doesn't bleach his SPS
12DX LED Build