what do u mean by screen time?. aftermarket support is excellent. developer rom will be updated every friday, usually by evening the update already available. the phone is rooted, no need to search around for the method of rooting.

as for custom rom, i can't seem to find anything yet but maybe later we can use cyanogenmod as previous devices. if u are mainstream user, stock rom is sufficient. there are plenty to customize. if u never use miui, some of the features which u might like including:-

- changing carrier name
- taking screenshot by using toggle icon
- easy sharing link for all apps including messaging, file explorer, contact, etc. if u notice stock android rom for other device sometimes lack sharing link
- easy backup features which u can save all apps and other item using one click
- easy to customize theme including homescreen, lockscreen, icons, fonts which u can access using themer app. currently they use online checking for changing theme. u can't easily make your own theme and applied, u need to register as a developer 1st. custom rom might bypass this feature someday, for example wiui rom
- easy cloud sync. u can sync separately using mi cloud and access your backup at https://i.xiaomi.com/
- guest mode which u can activate to hide pictures, etc if u lend someone your phone
- nice security features including virus scanner, junk file cleaner, manage data usage, blacklist and even power management which u can set sleep time during the time u wish to put your phone in sleep mode; for example between 12am - 6am where u put your phone in airplane mode, it can reduce battery life as well as manage your sleep without disturbance
there are a lot of other features that i missed. other ppl can add.