I have a Mi 9 and it has been draining battery using the official MIUI 12. I also got a lot of ads in the system apps, which I never can turn off all of them no matter what adblockers I installed. I got frustrated and desperate, so I tried out the famed custom MIUI 12 from Xiaomi.eu. They are very good in extending my battery and so smooth and sleek. I recommend this for other phones too, since this is a custom rom. You wouldn't regret!

since xiaomi.eu is sourced from china miui rom (just debloated) the version wont be updated anymore. my redmi note 4x is running on miui10 (android 7) i think thats the final xiaomi.eu rom you can get for this device. so yes netflix and some other banking app like mae wont work on this device.
it's under EOL (End of Life) Devices in xiaomi.eu website already. if you want to use banking apps i suggest you just change to latest budget devices.
if you want to install custom rom you can check xda, but you need to know how to tinker with the device if you want your banking apps to work.