The Planamic would be the furthest away from your preferred signature. They're pretty dark and without EQ, are a mess FR wise due to that rise at 4k hz and that sharp drop after. It's pretty jarring to these ears. They're also quite power hungry but they do produce a very clean , undistorted sound so ymmv but that is the consensus thus far.
Between the PX and EDC3 is a toss-up. Neither of which I would call flat, but the EDC3 gets much closer than the PX. It's pretty unoffensive and plays it safe tuning wise. They're not bad, just a little boring sounding and rolled off up top. But, they aren't peaky ever and smooth no matter what's playing. They have good ergonomics and accessories as well too.
Personally, I really enjoy the PX the most amongst the three. It has a mid bass hump similar to Sennheiser but has some energy up top to give you some shimmer and sparkle from instruments. They also have a good build quality and accessories and can be worn up or down. However, they're the heaviest of the group and are also power hungry. They'll sound ok out of a phone but with an amp/DAC or DAP you'll be rewarded with their true potential. They also have triple flanges (my weird preference) so for me they have the best isolation due to this. Normally, I'd say they're a bit bass light but only compared to the Planamic which is definitely tilted to the lows. The EDC3 comes in last in regards to the lows but they are the most linear overall, for better or worse.
Honestly, the PX matches the 1More the most out of the group but with more energy up top. I'd also vote them the best from ergonomics, accessories, and build but they're also power hungry so watch out for that if you end up with them.
I have all 3 and had the 1More's ages ago and the PX is the only one I regularly listen to. I gave the EDC3 to the wife and the Planamic I'm selling off. And while not perfect, the PX hits a lot of sweet spots for a good price.
Just my .02 cents.