Top panel case fans, one in, one out?

[The Third Thomas]

So I got a new case with 3 front panel intakes, and a single rear panel exhaust. There's room for 3 more 120mm or 2 140mm fans on the top panel. 

 

Since I have a Hyper T4 and an AM4, my cpu fan is mounted bottom to top. I'm planning on installing a 120mm fan above my cpu fan in order to exhaust the hot air more efficiently. 

 

I've heard (mostly heard) some things about airflow, and how it's important to have more intakes than exhausts, and with a new 120mm installed above my cpu there's 2 exhaust (2+ if you count my cpu fan blowing upwards) vs 3 intakes. So I'm basically going from +2 intakes to only +1 intake. 

 

There is no room for another front panel intake, so I was wondering whether I could install a second top panel 120mm as an intake, or would that disrupt the airflow and have other negative effects? 

 

^me trying to visualise^

[Guest]

I would imagine that creates some kind of turbulence in there, because then instead of going straight the air gets pushed by the air that comes from the top and it disrupts the airflow.

[WoodenMarker]

Having more intakes than exhausts is mainly for maintaining positive airflow which is only useful for reducing dust accumulation when the intakes are filtered. 

What are your specs?