Anyone could bring a clear explanation about bits/headroom in modern AVRs??

[Gedeon]

It seems clear that some bits are needed for bass management when LFE channel is present and source is 16bits.

Another bunch of bit is required to get headroom for RoomEQ gains, precision and filters.

And maybe another set to digital volume control

Source is usually 16-24 bits integer.
Dsps can work 32bits float
And at the end of the chain we have the DAC and volume control...

Any good reading or explanation for this ?

Thanks in advance.