I am not sure what to tell you as I can only tell you that those lights are only going to support a couple of plants each under each one. I would suggest just trying to pick and choose whichever strains meet your needs based on whatever criteria you are looking for I suppose.
I don't grow Northern Lights, not that most Northern Lights offered by any of these Seed manufacturers is real deal representation of the original Northern Lights anyway.. or Sour D, same answer btw.. so I can't be of assistance there with giving you advice on that.
If you really want to find a good mother plant.. Usually the way to go about it is pick one strain, run as many plants as you can of that one particular strain, select the best plant, clone her if satisfied with that particular pheno or run it again.. it sometimes can take a few seeds.. sometimes you might have to run a whole pack of ten.. but a pheno hunt can prove worthwhile to find a good mom if you want to run something repeatedly again and again. I have mother plants I have kept for years that are proven winners.. and it can take a lot of work and effort to find a good one sometimes.. or you might get lucky and pop one seed and hit the genetic lottery. With seeds you just never know.
You could sacrifice your yield and get a bunch of smaller pots.. one gallon grow bags, cram as many as you can under the lights and run all the seeds you can.. and do a little pheno hunt. You'll water the plants more often for sure. It'll be a little more of a pain in the ass. I'm kinda doing something like that now with 2 gallon grow bags and these Cheshire Kush seed plants from Alphakronik.. 8 females too out of a ten pack.. didn't expect that.. but I know in the end chances are, I'll have that dank ass heavy las vegas purple kush leaning or heavy Gobbstopper leaning pheno that I want. I'd probably be happy with either. Next run I can run whichever keeper I select real proper and get rid of the other less desireable phenos that present themself from the 7other female plants. Running seed plants can be fun.. it's the mystery of it all that I like about it.. but it's always more work.