Well, full ROM is not rooted, that's for sure. If you want to install it, do a backup before with TWRP on Micro SD. It is very recomended. If something goes wrong then you can restore your system.
For CLEAN INSTALL, on Mi Max 3/32 GB, I followed theese steps. By doing this, you will loose all your previously apps and data:
1. Download and Copy full ROM from first post on Micro SD (miui_MIMAXGlobal_V8.1.6.0.MBCMIDI_1e6706b520_6.0.zip).
2. Download and Copy SR3-SuperSU-v2.79-SR3-20170114223742.zip on Micro SD. Can be found here: download.chainfire.eu/1021/SuperSU/SR3-SuperSU-v2.79-SR3-20170114223742.zip?retrieve_file=1
3. Download and Copy Install lazyflasher-no-verity-opt-encrypt.zip (a script to disable dm-verity and forced encryption) on Micro SD. Can be found here: en.miui.com/thread-310923-1-1.html
4. Boot into TWRP.
5. Mount System, Data, Cache, Internal Storage, Micro SD.
6. Advanced WIPE -> Select Dalvik/ART Cache, System, Data, Cache, Internal Storage. Swipe to WIPE.
7. Install miui_MIMAXGlobal_V8.1.6.0.MBCMIDI_1e6706b520_6.0.zip from Micro SD.
8. Install SR3-SuperSU-v2.79-SR3-20170114223742.zip from Micro SD.
9. Install lazyflasher-no-verity-opt-encrypt.zip from Micro SD.
10. WIPE DALVIK & CACHE.
11. Reboot to System.
If device automatically reboot after step 8, reboot again in TWRP (by continuously pressing Power + Volume Up until vibrate and then release and wait for TWRP) and continue with step 9, 10 and 11.
Wait 10-20 min for first boot and continue with system setup. You will have SuperSU installed.
This worked for me, but I'm NOT responsible for your actions.
More about MIUI Global Stable ROM 8.2 Fastboot and Recovery versions here: en.miui.com/thread-508000-1-1.html (Changelog and Download links).