With the black STO, Maths, they're actually just cheap black faceplates you can buy and swap at any time.
Just fancy looking things, not necessary: https://www.modulargrid.net/e/other-unknown-materia-urania-maths-black-gold
Yes, with the FH-2 you have enough modulation sources: and if you incorporate it with your DAW you can assign CC numbers to the outputs and draw in your automation—any curve you can create. Including the expanders, no matter how you arrange them, 24 outputs is a lot for your case. I have no idea where you're planning on putting them all!
If you can describe the type of music you make or want to make or can compare it to musicians you're inspired by, other members with similar taste might have helpful advice on finishing your rack.