How do DAC filters like…
Fast roll-off
Short delay slow roll-off
Short delay fast roll-off
Slow roll-off
and NOS etc
Figure compared to EQ’ing?
I don’t EQ (really can’t be arsed just sell stuff I don’t jam with) but I do use two of the above DAC filters on my DAP depending on mood, IEM and genre.
Just interested in how the “filters” work and what they “actually” do as most sound pretty much the same 
In a lot of cases most of them sound pretty similar but I always like the super slow filters for old music. It smooths out old grainy recordings a bit and kinda reminds me of class a. Gets rid of a bit of punchyness but older genres typically didn’t aim for punchyness anyways lol. One of the byproducts of the filters I noticed was the 2nd and 3rd harmonics have a noticeably different texture to them, again, really subtle, but every once in a while stars align and the filters make a really nice difference.
Normally it shouldn’t make a difference for a single-DAC consumer-setup, unless you’re going filterless NOS, which is an incomplete design that fails at its job as a DAC, rolls off the highs by a lot and introduces undesirable ultrasonics and IMD.
http://archimago.blogspot.com/2013/06/measurements-digital-filters-and.html
https://archimago.blogspot.com/2018/11/nos-vs-digital-filtering-dacs-exploring.html
But it will make a difference in signal latency and the ability of a band to play in sync if you cascade multiple DSPs before the DAC and you’re using long-delay filters in each of them (normally more accurate), and that’s why stage sound professionals prefer short-delay a.k.a. minimum-phase filters (which is presumably also why iFi set that option as default, which I would say is mistaken when their DACs are clearly marketed to the home user, not the stage professional, who will know what to select anyway).
https://troll-audio.com/articles/linear-and-minimum-phase/
So unless you’re using filterless NOS, these filters “do nothing” vs. how much an EQ changes the sound.
One is a filter, it takes away things. The other shapes stuff.
The way a filter in DACs works is it takes whatever the DAC chip produced (= sample and hold) and fits it into the 20 Hz to 20 kHz range (= creates sound).
An EQ is like sandpaper (although it can be used as a rasp), it can not “mold” frequencies like a filter in the DAC sense does, it just modifies what is there.