/g/ If I will use cooler 120mm with 12V/0.2A in place where is

ofc I mean 120mm 12V/0.3A*

Your computer would consume less electricity.

>>54977471
I am not sure.

Cooler will consue 0.3A because how is it possible for a cooler to reduce from 0.3A to 0.2A?

I am not sure what effecti will be on cooler if you give him 33% bigger current

>>54977742
The 0,2 A fan will consume 0,1 A less current when operated at 12 V.

>>54977217
0.3 amps @ 12 volts = 3.6 watts and should mean that the resistance of the motor is 40 ohms.
-NOW-
0.2 amps @ 12 volts = 2.4 watts and should mean that the resistance of the motor is 60 ohms.
The 0.2 amp fan will use less watts of electricity than the 0.3 amp fan, that is all. The 12V/0.2A fan will probably be a little bit weaker than the 12V/0.3A fan, but you have not given me enough information to say for certain; there are plenty of other factors.
anyways
read up on ohms law if you don't believe me, it will make sense to you. you will only get into trouble if you INCREASE the power draw for your circuit if it was not designed for it, DECREASING will not harm anything.