Wow! Some of your comments are contradictory... and the AP1 V-shaped??!
So, is AP3 "V-shaped" or "midrange heavy"?? This is a contradiction.
I will saying this: If you're coming from the APM, the AP3 is clearly more bright, with more mids and treble presence and not having sufficient/'exciting' bass. If you're coming from AP3, the APM is bass heavy, with mids showing recession and veiled mids/highs.
I don't know the music you're listening for your opinions (the genres and the quality of the masters and/or recordings), but your comments of AP1/2, EP & AP3 are so different than how I hearing all this devices.
We've gone back and forth on the AP1, they are V-shaped to my ears if I had them fit to my preference; I more or less shove the AP/EP as deep into my ear canal as they can go and they just rest there in a very stable fashion. My ears are smaller, so that may or may not help that work out. If I rotate about the stem so the front grill point away from my ear canal, the V-shape goes away and I hear them how you describe them. Like I said earlier, this is the reason why we hear the AP1 so differently, it's a matter of fit. This also explains why there are some measurements (I linked to them earlier) that show the AP1 having a large mid-bass while others have it without one. Fit with earbuds (well any headphone really) will affect how the headphone is perceived and measured. The same fit issues could also explain our differences with the EP as well though I can't seem to find my EP to confirm this.
V-shaped or midrange heavy... it's both; it's not quite as contradictory as you make it seem. A V-shape normally just points to a dip somewhere between the bass and the treble. You can still make something that sounds very midrange heavy doing this, namely by focusing heavily on the upper midrange, scooping out the lower midrange, and then giving a subtle boost (or no boost) to the bass while leveling out the treble to taper off. The V is not symmetrical in this case, the left (low) side is lower than the right (high) side. In other words, I hear a V-shape due to a subtle bass boost in the mid bass (probably around 5 dB give or take; it's not
huge, but it's there) and a substantial upper midrange midrange boost which creates a V-shape with an upper-midrange focus creating a scoop in the lower midrange.
I will also note that Spatial Audio/Spatialize Stereo further's this V-shape by creating an almost boomy bass while just barely accentuating the upper midrange creating a more balanced V; Spatialize Stereo was on when I initially used my AP3 since that is my preferred setting on my APM. I shut it off at one point as well, I don't remember when. There is a chance that ear fatigue may have influenced my late night edit as well (I stated this though) since that also has a tendency to make things sound more upper midrange focused (and if something is already upper midrange focused, it makes it even worse from that perspective).
I do agree with you regarding the actual midrange balance of the APM and AP3, the APM scoops out the upper midrange and lower treble a bit much while the AP3 scoops out the lower midrange; they focus on opposite parts of the midrange spectrum. If you are coming from the APM, that will be polarizing. However, I've been listening to my Euclid and EVO more lately. The Euclid definitely has a slight V-shape tilt to it in a similar way to the AP3 (with respect to where the V is situated and how the bass is balanced) while the EVO is a warm sound signature (though some could rightfully also argue warm over neutral). Lately my APM have been used more in Zoom calls than they have for music, but I do put them on every so often for 15-30 minutes or so since they are in my rotation. I'm actually
not coming from the APM (reason why the comparison was
from memory; and a far memory at that since it's been a while since I listened without Spatialized Audio).
As for music preferences: rock, punk, alternative, acoustic versions of said rock and alternative, metal, pop, little bit of classical, a little bit of rap. My iPhone is generally on shuffle (so I get a bit of everything) using Apple Music 256 AAC. Fidelity won't increase with lossless due to BT (not that I could hear the difference wired).