I observed in case of Mi phones like Redmi Note 4 & Mi Max2.
We’re not able to disable Google Apps like Chrome, Play Music, Play Movies & TV, etc.
Please let me know, how to disable Google apps?
I will tell you how I achieved this on my Redmi note 5 pro:
Use adb shell to give this command:
pm uninstall --user 0 package_name
This must work, tested on miui 188.8.131.52
The apps will come back after factory reset
More info: XDA Developers
If you can't disable it normally in settings or the disable button has been greyed out for some reason then I'd suggest you'd follow this procedure given in this MIUI form thread: Disable Google Apps In MIUI 8 (and 9) which I too confirm to be 100% working (tested).
Install Quickshortcutmaker from Playstore
Select normal search - under input box type manage apps and click search
NB: No root is required!