I use the Jiffy seed starters:
https://www.walmart.com/ip/Ferry-Morse-jiffy-J425-All-In-One-Greenhouse-25/1762496
And then I transplant to it's FINAL container after about a week (assuming they popped) - I don't do this multiple transplanting thing that people do. Basically, this guy pretty much does what I do:
Except that I actually rip the netting off the pellet if the roots haven't broken through them yet. If the roots have broken through already, I'll leave them on.
I actually have a Pineapple express #2 in the box right now. It's about 20" tall at the moment - after approx 1 month - and has been a no-issues plant at this point. It's sitting in a fresh bit of Happy Frog and hasn't needed any additional feeding at this point. It's actually a pretty perfect looking plant right now. I only plan on letting it grow to about 30" before I force it to flower. It should still grow another 30" or so during the flowering stage but I have no intentions of letting this thing get to be 8 feet tall LOL
So keep that in mind with your photoperiod strains - you can pretty much force them to flower whenever you want - and they'll still grow another 75 - 120% taller during flowering (assuming you weren't already close their max size - I would say on average, photoperiods that I've grown have doubled in size after I force an early flowering). That PE#2 you have can get taller than 8 feet and you only got 6'11" to work with; and you don't want the plant getting too close to your lights as you'll just start burning the leaves and buds. Personally, I don't let my plants get closer than 20" to my lights and prefer to keep them 30" away. There are obviously other methods of controlling your plant height but, for the most part, I control it by forcing it into the flowering stage when it's about half the size I want it (unless its normal max height is acceptable to me; or it's an autoflowering strain, in which case I have no control over it).
Obviously, if you want the largest harvest you would let it veg until it's done growing.
If I was only working with 6'11" ... I would approach my grows as if I had 5' of usable grow space and plan accordingly.