I always use 452X for cables, and Im pretty partial to BCY products. Not saying Brownell, etc are any better/worse....its just BCY 452X has given zero issues to many people, and I wish not to put extra money into multiple brands.
The 452X is extremely stable and only accounts for a couple fps, if any. To me, the stability far outweighs the couple fps that you might get with 8125. Plus, you are much better off with a stable cable, and the cable doesnt factor into speed difference. If someone really wants the extra 2 fps, I might make a 452 cable with a 8125 string.
As for strand count and serving size, I'll usually match up diameters to the OEM size that the bow was designed with. Most cases is a 24 strand cable with .014 Halo end serve. The only time I deviate is when Im trying to get something different out of the bow....stiffer wall, more holding weight, etc. Just beware when you change diameter, you may change things like max poundage, letoff, etc.
Good luck.