How deep do you want to go, Jim? This is a very involved question and answer. BUT, as a baseline, this is why I am such a massive proponent of 'tunneling'. If you can expertly tunnel your pitches, the shape of the pitch itself is even more impactful. Precisely why RHP's Manuel Rodriguez and Melvin Hernandez are so successful despite their low velo. Their shapes are awesome - Hernandez's change-up is <chef's kiss> Rodriguez's slider is <chef's kiss> because it all looks the same leaving the hand in the exact same locations. Uncanny. The tunneling challenges RHP Ryan Birchard faces with his uber-viloent delivery is precisely why the shapes of his pitches - tho quite awesome - aren't as effective as they could be. It's easy to see a ball is a ball in his case.
SO, back to the original question: how deep do you want to go?
In general, tho, I think it may just be easiest for you to think in terms of:
(1) Speed/Velo
(2) Horizontal Movement
(3) Vertical Movement
(4) Arm Slot
(5) Release Point
(6) Extension
The consistency (more important in some aspects like Arm slot, release, extension) and range (more important in speed/velo, horizontal, and vertical) of all of these impact the the effectiveness of a pitch. Hopefully, this is a good starter?😅