As for the sound, I'll try to compare it with my SR80s. To my ears I've always thought SR80s are a sort of balanced dark sound. No sparkle up top, no sibilance. Vocals fairly in your face but not clear as I'd like (perhaps bordeline hollow, but I don't mind it) with an OK amount of bass to me. I actually much prefer over ears to on ears, but still ran my SR80s as my daily drivers at home for a while before trying other stuff so I do have a bit of a soft spot for them
The M2s have no sparkle up top either, however have much more bass, distant vocals and can be quite sibilant. I'm guessing they were going for a mass market v-shape? I don't know I could be wrong, but when listening to "Lose Yourself to Dance" by Daft Punk all I hear is the bass guitar overwhelming everything, and the rest of the track just takes a back seat. One of my usual sibilant test tracks is some good 'ol Kpop, "Heart Attack" by AOA. If I can make it past the first chorus and verse then we're usually good, but the M2s were shredding my ears within seconds lol. But perhaps I'm being to harsh, so I put on some tracks with little to no vocals. Listening to "Kerala" by Bonobo and "Baralku" by Emancipator the extra bass and overall warmth were welcome, even if the little effects in the track sounded a bit tinny. Something like "Everything At Your Feet" by Odesza sound fun also and squeezes by OK because the vocals are so intentionally filtered anyway.