I've been mulling over stack size and how if effects play in NU NL. I'm going to post my thoughts. Please let me know if I'm way off.
Let's look at two hands - 97s, and J7o. Both these hands have roughly 50% preflop equity against ATC (actually a hair less, 49.5% for 97s and 49.9 for J7o).
When stacks are deep, a wet flop connects really well with a hand like 97s. Even if you don't have the beat hand on the flop 97s gives you a lot of ways to improve to the best hand. But in deep stack play, if you flop top pair with J7o and you get played back at there's a chance you are gonna suffer some bad reverse implied odds. So in deep stack play a hand like 97s can be played aggressively, but J7o should be played more "small ball."
When effective stacks are shorter it's the other way around. Top pair with J-rag can be played aggressively, while connector-ish cards should be played more small ball.
I'm kind of excited about both hands you mentioned.
T5o vs 63s? gogogogo
I'd open 63s with full stacks but would fold T5o. I'd open T5o with baby stacks but would fold 63s. I've had this loose theory floating around my mind for a while now regarding hands that derive much ev from late street bluffs. Of course, if we don't have the stack with which to bluff the late streets, then a hand like 63s is likely unprofitable.
I'd open J7o Deep. I think 97s is a great hand if there is a wet flop. But I think i'd rather play my J7o aggressively with top pair. Than small-ball with it. And I'd rather small-ball with a 97s. However I keep my opp guessing when playing HU. Prefer loose play.