Well if you mean the in the image I attached, the ypao detected LPF would be in reference to the LFE channel. The bottom graph. Basically you can lpf, the top of the LFE signal. This is irrelevant to music since there is not a .1 channel in music, but only movies.
The extra bass I have not used for a long time. I have tried it with yamaha, Onkyo Marantz and pioneer. I don’t like it at all as it only serves to make muddy bass. Ymmv of course.
Using the extra/double bass feature you can usually select a XO filter since the mains and subs get a duplicate signal. In reality though it’s more of a HPF for the mains. Again, IMO extra bass is a mess, and using it for movies is a good way to destroy speakers.