it's too early to speak / evaluate performance, as just past 12hrs since install it (once released)
till now all good. same smoothness, responsiveness and behavior like in last month version (xiaomi.eu beta 20.9.17) which was perfect A10 MIUI12 for me !
gesture works (i use native launcher), i have no need for dual apps so can't comment on that, all other nice w/o visible bugs (CoC, simple weather widget, Fiio Music, etc.)
no battery drain (2% drop overnight in ~10hrs) so doze works fine;
notifications sharp - gmail, banks, sms, vip access, ... all i have - but here it mainly depends on each flavor setup (!)
no need to format data, just wipe cache + davlik cache before and after flush; haven't delete the .../package-cache but this does not seem to impact me;
i use dark mode and all apps comply
, the only issue is that the options on extended power down have icons too darkened (almost not visible - prob. a bug).
as such i must say: great job
xiaomi.eu team ! thank you !