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For touch, many people had said that touch has improved in 10.3.4.0 but there are some people who are saying it got worse.
You can try beta rom since it has more improvement on touch.
Refer this thread for more information regarding beta rom but please use browser to open link (community app does not support opening link now.) https://c.mi.com/thread-2123980-1-0.html
For overheat, can you give the temperature?