Well, I didn't spend much time with it, so these are very early impressions with the stock tips. The xduoo ep1 is warm and bassy. The bass is quite big and can be overwhelming but at least it's relatively tight given its amount, which is a pro as for me loose, soft and hollow are extremely unwelcome traits for a low end. The mids are warm and full with a decent amount of detail. They lack transparency but that's usually the case with thick note presentation. Both male and female vocals have good presence.The highs aren't peaky and have a good amount of sparkle but lack some shimmer and air on top. Overall, the presentation is full and enveloping but a bit on the intimate side.
To be completely, honest aside from the overall sound signature, which might not be exactly my preference as I prefer more flat and neutral sound, the xduoo ep1 is definitely good for the money. It doesn't have any glaring flows like slows and soft bass, sharp peaks, artificial treble etc. Aside from the amount of the low (which for some will be welcome)m the ep1 is actually a competent iem and I've heard worse in the same price range and above, so unlike some other iems I've bought throughout the ears and disposed of quickly, I can't say I regret getting it.
I'll have to burn the ep1 in and do some extensive tip rolling but if the bass levels a bit and the upper treble opens up it will be a positive change. Also, experimenting with tape modes on the vent holes is totally an option as plugging them with fingers definitely removes a lot of warmth and reduces the bass (IMO too much when completely sealed but someone might tinker with that). And again these are early initial impressions