when you say ‘Q’ on a HPF, do you mean slope? HPF’s can have lots of different slopes from very gentle to extreme. The positives over regular eq, in my tiny brain, are;
An amplifier needs WAY more power allocated to say 30hz than 3,000hz and odds are very good your cab can’t reproduce 30hz anyway. So why waste wattage for something you can’t hear? With a decent HPF you simply crank it up until your low end noticeably shrinks, then back it off a bit from there. You just gave yourself good speaker protection and headroom from your amp. Though like I mentioned, I think it’s way more critical on upright than electric. Part of that could even be the differences between a piezo and magnetic pickup for all I know.