MiMix2S works well. I use unencrypted phone, magisk with some modules. .
My week 2 week update method (dirty flash):
- clear phone unnecessary data, clear mi security app and setting-> storage cache clear.
- rebooot to twrp recovery (use the latest!
https://twrp.me/xiaomi/xiaomimimix2s.html)
- unistall magisk with uninstall zip
(
https://forum.xda-developers.com/apps/magisk/official-magisk-v7-universal-systemless-t3473445)
- clear only dalvik cache
- (not needed but recommended) backup only data partition because rom owerwrite boot, vendor, System
and more partitions (unnecessary)
- flash new rom zip files with 'zip signature verification' - if image file bad, the flash does not start
- reboot phone (dalvik cache recreation - it takes more time to boot -)
- check setting menu, new features to set up, (re apply if use custom theme, (visual mistakes occured)
- reboot phone again to twrp recovery
- Flash magisk zip, and reboot
- install favorite modules, adaware apps needed 'systemless hosts' in settings menu
- reboot again to work installed modules
- add apps to 'superuser', and 'magisk hide' if needed
I do this week by week since November 2018, and apart from a case (that weekly update was missed), I had no problem.
I can't comment on Google's pay problems because I do not already have one in my country.