For the first time after messy so so so much around roms and kernel, I finally found the best combo for my usage.

My combo: Nothing fancy, just MIUI8 Global Dev Official ROM 6.7.21 (6.7.29 got battery drain bug), ROOTED with temporary TWRP, so basically i have no recovery now. And remove some of the google apps that I dont use. Installed Kernel Adiutor to monitor my deep sleep state to see if everything is normal. Oh, wifi is on and off depend on my location availability.

My humble usage:
1.) Facebook (scrolling and video streaming)
2.) Instagram (scrolling and video streaming)
3.) Between (couple apps)
4.) Whatsapp (Lots of active group chat)
5.) Chrome browser
6.) Taking pic here and there and edit with snapseed then share it with my whatsapp group.

Other installed apps but less usage: Qatar Airways (my gf work in qatar airways so i need to track her arrival and things, this apps has push notification so maybe will take off some of the battery), Snapseed, Spotify, KLSE Screener, Shazam, Skype, FB Messenger. (all this apps i had restricted with miui battery optimization, except the qatar airways apps)

My result of battery life?

100-1% Battery is about 10HRS SOT. All i can say is, it's the best so far. Of course, I don't stop here, I will make this backup with TWRP Alka (which it can backup all file to have a perfect complete restore for future) before I try any other ROM in the future. All my important notification arrive in real time, i dont freeze here and there anyhow. Just as how a normal phone should function. No gaming thou.

EDIT: Sorry no screenshot, not convenient to post one due to my work place...

Try reset the phone setting, if still cannot then have to report to Mi Malaysia
Mine front and back camera both working with fingerprint scanner

very hard to find local set good price

If flash and reset I heard that in miui there is a feature age you can backup all apps and data offline.
Is it true? Reliable?

I have to much apps and data. Downloading again will take much time and data

Do you official unlock bootloader first?

So far no issue on 7.5.3 all tuning good with best sot... All time all 4g and wifi ..  use for. Fix Facebook messenger and browser can easy hit 7 hours sot and above..

AP set might have different ROM installed.
The one I got after buying has Swiftkey has default keyboard and I can't seem to find OTA update to 7.5.3.
I downloaded 7.5.3 manually and then choose the package so it says something about different version and the phone had to reset to apply the update package.
The update I downloaded comes with google keyboard and pinyin input.

I think you can ask the shop to flash to latest ROM but I bought it from gemfive so can't do request.

yeah..im fan of xiaomi phone..usie redminote 3g..drop like gila2 but still good working..
i no expect xiaomi product quality good b4 wor...now looking for rmn3pro..any seller here? sell chip2 2me lo..hihi

So far no issue on 7.5.3 all tuning good with best sot... All time all 4g and wifi ..  use for. Fix Facebook messenger and browser can easy hit 7 hours sot and above..

I had batt drain issue then I just simply reset phone. Now all fine

AP set might have different ROM installed.
The one I got after buying has Swiftkey has default keyboard and I can't seem to find OTA update to 7.5.3.
I downloaded 7.5.3 manually and then choose the package so it says something about different version and the phone had to reset to apply the update package.
The update I downloaded comes with google keyboard and pinyin input.

I think you can ask the shop to flash to latest ROM but I bought it from gemfive so can't do request.

Mine on 7.5.3...camera shot front and back with fingerprint scanner works fine.
Everything is fine...normal use can get 6-7 hrs sot.. Wifi and data..

Err...how to see that 'history' battery graph arr?

yeah, correct... not sure why we have to do this... hopefully new update can fix battery issue... actually why android phone always face battery drain inconsistent since lollipop... i dont remember this problem in jellybean thou...lol