[Xiaomi Mi 4C] xdadevet:
The Xioami MI 4c seems like a good fit for you. My iPhone-centric friend said that my phone (the Mi4c) is the Android phone he hates the least :P

It is very easy to flash an AOSP based ROM (what you called "Native Android") such as CyanogenMod 13 on the Mi 4c. However, it might not be necessary as there are good debloated ROMs available based on MIUI and MIUI has a lot of nice unique features. There are instructions on how to do this on each thread, but message me if you have problems.

MIUI (and ROMs based on it) has far superior camera quality than anything else available for this phone. It also has a lot of manual features (manual focus, exposure, sharpening, saturation, focus tacking, numerous filters), though its long exposure is limited to 2 seconds and focus bracketing can't be manually adjusted. However, audio performance out of the auxiliary port is much better in AOSP based ROMs (MIUI has some audio processing that messes up the audio). Keep in mind that in general the phone feels more snappy on AOSP based ROMs, but in both cases there are very little to complain about.

My recommendation is that you try the MIUI ROM from this site (it is clean, debloated, and properly translated) for a week:

https://xiaomi.eu/community/threads/6-9-8-9.34062/

then switch to CM13 (the nexus-fy version on this site) and decide for yourself which you like better.

I didn't find any bugs in these ROMs, but you'll have to read the respective threads to see if there are problems and if they have been fixed (and how to fix them if it isn't already). Luckily it's very easy to switch ROMs if you encounter problems.

All the tools necessary can be found on this site, but you might need to install "Flashify" from the play store in order to get a custom recovery on your phone if the conventional methods fail (ADB tools).

Things to keep in mind:

- The back cover is nice to touch but scratches easily, so either get a cover or keep in mind you can replace it if you have to.

- The front glass may be vulnerable (no official protected glass is disclaimed), get a tempered glass screen protector.

- The volume and power buttons are plastic

- Battery life is decent but not great (about a days usage, 5h screen on time)

- Camera is great in medium to good light, average in low light - feel free to ask samples

- Audio is great out of the port, and good from the speaker

- Display has stellar contrast, good colour, average brightness and is a bit difficult to read under direct sunlight

- Performance is generally good (there are some hiccups), but by far the best for the price

- The 16GB model is half the price of the 32GB model($110 vs $220 ), check Kimovil to get the best deal (I've used Geekbuying reliably through the years)

- Build quality is good otherwise (barring the above issues). I've used this phone brutally without a cover and it never gave me any problems.

- If size doesn't bother you too much, the Redmi Note 3 Pro is a great alternative. It costs $150, has better performance, awesome battery life, 3GB RAM, 32GB storage and a micro-SD slots. Its cons are you lose out on the camera and audio quality, and the display's contrast isn't as good (1000:1 vs 1600:1). It also gets lots more love from Xda and already have an Android 7.0 Nougat ROM.