fast charging vs normal charging? battery efficiency

[KirKirKiran]

Can i improve screen on time if i charge in normal charging mode.? Any difference with fast charging? 

Also I wanted to know when to start charging and upto what percentage to charge for battery safety and efficiency 

[IcyJay30]

i keep my phone between 20-90... also fast charging will only affect battery incase its overheating....
i don’t think overheating will happen in winters or charging in AC room(summers).