Sorry but i am not an expert audiophile, i just like listening music.. I dont understand what IEM is.. I will use only in-ear headphones, nothing else.. And i dont know how lg v20 sound.. I only have an oppo 7a and i think the music is ok with dirac sound.
I dont wanna use adapters, amps or anything else to improve the quality, cause i will have the phone on my pocket while running. Just the phone.
Then anything in the list would work totally fine for you ^_^ just choose whatever you can find easily in your country.