Fluctuating fps in-game, expected benchmark

[Cheerleading]

I bought a 2nd hand PC and added a few bits of my own components to create this build:
i7 6700k (kept turbo boost on so can reach 4.2GHz)

NZXT Kraken X61 Water Cooler

Asus Maximus VIII Ranger 
Gigabyte GTX 1060 3GB

Corsair Vengence LPX 32GB DDR4 2666MHz
EVGA 750W G2 80+ Gold
Seagate 1TB HDD

SanDisk SSD PLUS 240gb

Windows 10 Home 64 Bit

 

I updated my GPU driver, CPU driver, changed PSU power plan to high performance, and benchmarked it with the following results:
Cinebench: 103fps, 860cb

Heaven: 85fps, 2144

I jumped into a game of csgo & overwatch and found that my fps would fluctuate; dip down to 30-50fps and go up to the expected 120+ fps.

CSGO settings: 4:3, 1280x1024, max video settings (motion blur & vertical sync are disabled)

Overwatch settings: 16:9, 1920x1080, lowest video settings except for render scale: 100% and texture quality: medium

 

My GTX1060 felt much smoother in my old pc with an amd fx8320, coolermaster 212 evo, gigabye 970 gaming mobo, 8gb ddr3, 600psu. 
Anything is appreciated thanks!

[Fasauceome]

Increasing your settings might deliver more consistent performance. Try increasing to 1080p in CS and turn all details to medium in OW with 100% render scale.

[Cheerleading]

13 minutes ago, fasauceome said:

Increasing your settings might deliver more consistent performance. Try increasing to 1080p in CS and turn all details to medium in OW with 100% render scale.

I did them but I still encountered the same problem. I noticed that it was only when I moved my mouse (vertically & horizontally) that my fps dropped in csgo specifically. Overwatch felt like there was some mild input lag but I'm not sure if that's just due to the poor fps.

[Fasauceome]

2 minutes ago, Cheerleading said:

I did them but I still encountered the same problem. I noticed that it was only when I moved my mouse (vertically & horizontally) that my fps dropped in csgo specifically. Overwatch felt like there was some mild input lag but I'm not sure if that's just due to the poor fps.

Interesting, reminds me of an issue I had where game lag was tied to GPU fan speed.

Did you update your USB/chipset drivers?