Going off spring rates alone to gauge how harsh/firm they are doesn’t tell you much at all. You have valving and fluid used also to consider.
The springs in my current setup are 15 mm front/9 mm rear and are much better at soaking up a bad road than a set of “softer BC’s” (which feel like you have railway sleepers as suspension) and even Nismo S tunes.
You get what you pay for here and a $1099 set isn’t worth the box they come in. Might be 36,000 way adjustable but it’s hard, hard, hard, harder and hardest.
Bilstien PSS9’s and the Ohlin DFV’s are probably a good place to start or as you have already said, the guys at MCA.
FWIW, I’ve had stock, Nismo S tunes, Nismo R tunes and the current setup which is Modified PSS9’s.