I would probably start at the difficulty level that most resembles the AI strategies you want to see.
For example, if you like the way the AI pitches to you on Veteran, I would start there. Sliders can't really address tactical decisions like who to pitch around, etc (to my knowledge anyway - strike frequency is about the only one that handles it and that's just on "early counts"). That's more the domain of hitting difficulty (higher = "try to get you to chase/swing at pitcher's pitches" and the reward can be more walks).
For the contact and hit type - if you're not missing too much and just getting too many poor results, I would try raising Solid Hits and leaving the rest alone. Solid Hits tries to "normalize" the results by bringing more "near the middle" trajectories instead of the very grounder or very fly ball trajectories (i.e. choppers and rollers/pop ups and sky high fly balls).
Be bold and audacious with it. Don't be afraid to go to 10 and see what happens (maybe make a copy of your franchise/season so you don't screw up your main game save(s) or start a new test game as a "sandbox" of sorts).
You could also try raising Contact and leaving everything else alone. Contact does impact the chances of getting Normal/Solid contact vs Jammed/Pulled Off, which impacts contact type. However, you can still get a bad trajectory still and might impact other things like too few K's, too high batting averages, etc.
That's why if contact rate (i.e. how often you swing and miss) isn't a problem for you, I'd lean towards tinkering with trajectories over Contact. It has fewer side effects and is easier to undo/further tweak.
Timing is also a factor - since being early can cause more Pulled Off and late can mean more Jammed contact and the Timing slider impacts how wide the overall window is. But even then, not all early swings result in poor contact/swing labels and trajectory still determines the hit type.
For specific sets to try, I can't help you out there
tl;dr: Try Solid Hits first, don't be afraid of "big numbers", and start on the hitting difficulty that causes the AI to pitch you the way you like.