[Huawei P9 ROMs, Kernels, Recoveries, & Other Devel] zgfg:
Long story, tried several Chinese Android devices over the last 4,5 years (it was kind of my hobby buying/trying them)

1) Cube Talk 9X , powerhouse tablet at its time: 9.7 in with 2048x 1536, 32/2 GB, 10000 mAh, MTK 2GHz octacore

I learnt a lesson that MTK rarely provides kernel and driver updates, hence devices cannot be updated to newer Android versions. Also, their chipsets are power hungry and high Antutu benchmarks cannot be fully trusted.

Stuck at KK, but I'm using custom ROM Atlantis 2.0, something like yours here: stock based, debloated, prerooted. With Xposed and stuff it works excellent. There are still other happy users on the Spanish and Russian forums.

Using the tablet every evening at home for browsing, mails, etc (wtiting this now from Cube).

2) Elephone p3000, again MTK, also KK. There was never any software update and no custom ROM. Still functional (it did have some glitches) but lost in a drawer at home ;(

3) Elephone p6000, again MTK, stuck on Lollipop, although there were CM custom ROMs and Russian hackers still develop/maintain AOSP MM and later N custom ROMs (tried but switched back to the stock because of stability and performances).

Extensively used by my daughter for two years (several months as dual SIM phone). She returned me with broken display and broken battery cover, but phone is still fully functional except the unreliable Power button.

4) Meizu m2 Mini. One more MTK, with MM.. Meizu was providing beta and service updates every month. I liked some Flyme concepts (single Home button servng for everything)) but was never able to setup background notifications to properly work for all needed apps (GMail, WhatsApp, Viber, etc - one or another did not work in deep sleep).

Played with root and stuff but eventually sold the phone.

5) UMI eMax Mini. Snapdragon but also stuck at MM. My son (and me) liked the phone, but after a year WiFi stopped working (you can't turn WiFi On anymore). Tried hard reset, flashing two stock ROMs and CM custom ROM - no avail. IMO it's hardware error, maybe a loose contact to antenna or so.

Everything else runs smoothly (returned back to stock, with root, Xposed, etc), but without WiFi is hardly usable, hence we use it as an 'emergency' home (mobile) phone (instead of the unsubcribed fixed line).

6) Ulefon Metal. I liked the phone and its AOSP MM (got it rooted with stuff), but after 1,5 years my daughter gave me back with USB connector dead - cannot be charged anymore. Dead phone.

‎Don't know was it her fault (laying on couch while charging the phone...) or due to cheap/bad hardware like the dead WiFi on UMI. Similarly, I don't know if the unreliable Power button on her former Elephone was also due to physical missuse or due to cheap parts and bad QA in production.

There are no (official) service shops for the no-name phones, or they don't want to repair if phone was bought directly from China over Internet. Sending back to China for repair (even for warranty) is costly and risky.

7) Xiaomi Redmi 4 Prime. My son does not give me access and to play with ROMs, hence cannot say much except that he had no complaints over a year or so