Can I change some but not all Apple keyboard function keys (dim vs F1, bright vs F2)? I want to override F1 and F2 behavior, since I have external display and Mac can't control display's brightness. The rest of the keys should retain their non Fx

I know about "Use all F1-F12 keys as standard function keys.", but I don't want to change all of the keys to be F when pressed, just some of them. (For me single press music and volume control is necessary.)

Is there a way to pick some of the function keys to default to numbered function instead of the "Apple" definitions system wide?
You can use FunctionFlip to change individual "special" keys back to their function key value.