Question 1

Corsair Hydro Series, H115i PRO  since these fans are 3pin will they work like power fans speeds?

Accepted Answer

Yes they will work and still be controllable.  The difference is that 3 pin fans use voltage difference to vary speeds while 4 pin fans use a PWM signal to vary the speed.  The only draw back is as it slows the fan using voltage the LED will gradually dim the slower the fan spins because of lack of voltage where on a 4 pin fan the LED gets constant voltage and will not dim as the fan slows.  If you want a better 4 pin option I would recommend the Corsair ML140 LED fans.  I have 2 of those on a H115i and they are great.

Question 2

I want to pair this with two Noctua 140mm. These fans would be on the bottom pushing air out. With Noctua helping push the air out. Would these be a good setup for what I plan? Want to run these at around 800 to 900 RPM(NZXT Kraken X61).

Accepted Answer

With this case you the bottom row and front side bringing air in and top and back side blowing out, this will give you better airflow 
But noctua fans are very good quality

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