depends on who's northern lights you have. If you have Sensi Seed's, it should stay shorter and compact. Dense buds, super frosty but not crazy tall. I have seen other breeders NL get much taller.. I usually do 16 NL per light in 7x7 pots (1000watt light covering a 4x4). I have tried to grow them out larger and do less per light but I had the best luck and largest yields doing 16 per light. I only vegged them 2 weeks and I averaged 2.2 Ounces per plant. When I grew out 9 in larger containers per light and vegged them a month, I averaged 3.2 ounces per plant.
With LSD, it really depends on the pheno type you have. I love growing LSD. I am growing some right now in my garden. I have grown a few different types of phenos with LSD and The medium height pheno that ends up around 3.5 feet tall is my favorite. The real tall pheno wasn't as good in my opinion. If you are growing the shorter pheno, I would veg for around 4 weeks, and I would run 9 per light in 3-5 gallon pots. I run coco.
Northern Lights isnt super picky. It doesn't mind higher garden temps compared to most strains. It seems to like its nutrients so I feed it a bit heavy (1200-1400ppm). If you want to promote color change, it will turn colors with colder temps when lights are off.. LSD is a pretty easy plant that doesn't seem to picky about many things. I go pretty heavy on the nutes with LSD as well as it seems to like a heavy feeding. LSD will give you some funky colors if the temps drop into the mid 60's when lights are out. Never had any disease issues with either except with Northern Lights once. I got some budrot with NL once a few years ago. I think I had a corner spot with poor air circultation and it wound up giving me bud rot in 2 NL's once.. I have never had any bug, disease or any problems with LSD... The hardest part with LSD is trying to find the keeper pheno.. Good luck..