DACs generally use a filter that sharpens/does not sharpen and is so-called slow/no-slow. The RME ADI FS-2 DAC, like others, offers all four possibilities (and a nearly no-filter option, NOC). I hear some differences, but they are small.
The RME and some other DACs also have DSP circuitry, which offers some equalizing. In the case of the RME, five separate frequence bands of adjustments. These can make a big difference. I don't use equalization for room correction (curtains, sound panels, and speaker placement instead). The EQ is great for improving your-speakers-in-your-room. I found what I like by trial and error listening.