All three included fans are 140mm. I think the answer to your first question is: yes, it is possible, but you will need to move the included front fan to the top. There is room for either 2x 140mm fans or 3x 120mm fans on the front. So if you move the included front fan away, then you can install 3x 120mm fans on the front. There is a nice picture about fan placement at page 10 of the user manual, PDF here: https://www.bequiet.com/admin...

Oh and what size is the exhaust fan?