Re: Whats the best PH for strength?
For strength alone, and ideally low to no sides, I reckon the product you've linked would be a good choice used preworkout. I'd try 2 caps taken an hour preworkout at first, then perhaps run 3 caps if after 7/8 workouts I didn't see much benefit in the sessions. 3 caps would likely be the sweet spot for many I would guess.
Assuming you have days off between training sessions and ideally train 3 or 4 times a week, even at 3 caps the dose shouldn't be a worry.
I've ran SD alone in this way to good effect for strength at 30mg pre-session (no significant mass gain to speak of on this basis, though that is of course diet dependent). I've also ran dienolone in that way alongside a test cycle and seen benefit (@ 90mg iirc). Combined together in this product I would imagine a good chance of some strength increases in the sessions.