I’ve never trusted those presets and still don’t. If you’re sure you need EQ I’d make the adjustments manually.
I listen to a lot of old mono jazz recordings that lack sufficient bass and high end, so I tend to boost both ends a bit, especially the lower end. But if you go too low it will sound “boomy” or—even worse—overload the speakers or overdrive the subwoofer. If the bass boost overlaps too much with the midrange it will sound “boxy” or “nasal.” Too much high end will sound screechy or strident, and if the recording lacks those frequencies to begin with then all you do is boost the noise levels, which increases hiss.
In general too much EQ is worse than none at all. Be very judicious in how you set it. When in doubt keep it flat. Also keep in mind that both old and new recordings are often boosted when the master is mixed or transfered, in which case you might actually need to CUT one end or both ends to maintain fidelity.
The “classical” setting is usually fairly flat, so least likely to ruin the sound. The “loudness” setting is meant to compensate for low volume levels, to overcome a limitation in human hearing. Sound systems used to routinely put loudness compensation circuits into analog hardware, but that’s hard to find these days.