I5 6600 + RTX 2070 - Low FPS

Hello, recently I wanted to upgrade some parts of my pc and I got an RTX 2070 for a good price and a Samsung 144hz monitor. My PC parts are now:
i5 6600
RTX 2070
16gb RAM
I know my CPU is not the best and should be upgraded but I was hoping the 2070 would be a huge leap from my 960 and give me stable FPS for playing in 144hz until I can save more money for a new CPU. What im experiencing with Overwatch mostly is a frame rate flactuating from 110 fps to 250 fps. In team fights it’s between 110 to 140-150. These frame rates are with settings on low-med-high it doesn’t even matter what I change them to the difference is minimal 10-20 fps gain/loss. There is no overheating or anything. CPU Usage is at 96% - 100% while playing and GPU Usage is at 40% to 54%.
I’ve tried the following: ( In no particular order )

  1. Formatted my PC - started fresh.
  2. Optimized settings in Nvidia Control Panel
  3. Updated BIOS
  4. Changed Physx to GPU
  5. I messed around with all settings in Windows that allow for more performance, following guides etc.
  6. I tried upscaling to 1440p so the GPU gets more usage, still the same.
    Plus some more procedures I forget right now, I’ve been trying to figure out a solution for a week now.
    Is there something else I could do or is my CPU really bottlenecking the GPU this hard.
    I find it diffucult to believe that I could get 120 fps stable on low with a 960 but with a 2070 I can only get 140-150 fps mid-fight with the same settings.

I’m in the exact same boat i7 8750H (undervolted slightly to help with thermals) RTX 2070, 16GB of RAM, and a NVMe SSD. No matter how I optimize my frames will begin to cap @ 120. I’ve updated, rolled back, tweaked settings, reinstalled, and nothing will give me a stable 144