Here's my setup:

Alpine CDA-9884
JL Audio 500/1 amp
Alpine SWR-1243D Type R 12"

What if bass equalizer (Q, center frequency, boost) is configured in both HU and amp? What effects occur?

For example, having HU: Q (4), cf (60hz), boost (+4) and amp: Q (1), cf (40hz), boost (+8). Will they cascade or something? I’m sure one doesn’t have control over the other. Possible distortion?

Also, is there a rule of thumb on how high to set bass boost without damaging the sub?

I have input sensitivity at 2V, which matches the preamp output of the HU.
I have bass equalizer configured though the HU. (Q - 4 wide, Center Frequency 60Hz, Boost +5)

Bass Level: -7 to +7 (-14dB to +14dB in 2dB steps)
So, I'm at 10dB.

Bass equalizer on amp is all off.

Will my sub eventually tap out? Are there more appropriate settings?