I am currently running the nVidia GeForce rtx 2080. 

For gaming that cpu i7-9700k is already the top gun in this model.  there is barely an iota of gain to go to i9-9900k.  When gaming performance is not as good as you want, consider a faster gpu first before upgrading cpu.  Which gpu do you have now?  I would compare your cpu+gpu benchmark with others playing same game to have better grasp of your pc performance.

http://blog.logicalincrements.com/2019/02/comparing-i9-9900k-i7-9700k-8700k-gamers-gaming/

https://www.gpucheck.com/game-gpu/call-of-duty-modern-warfare-2019/nvidia-geforce-rtx-2070-super/intel-core-i7-9700k-3-60ghz/

You should get very good fps on high setting for i7-9700k + 2080.  The benchmark link in last reply is for 9700k+2070 for COD modern warfare, which should be similar game to Cold War.  What is your game settings resolution and fps?

Would make a big difference for content creation / video editing where you can put those extra threads to use.

But yeah, definately not a cost-efficient upgrade 9700k to 9900k for just gaming you wouldn't get much benefit.  Benefit depends on intended use.

I run all my in-game graphics settings on high, resolution at 1920x1080, and 144hz refresh rate. My fps bounces between 70-90 in multiplayer, and 55-80 in zombies. Is there just a setting on my computer that I need to change because I feel like this setup should  be able to perform much better than it does in game.

1920x1080 is 1080p. You should get on average 208 fps at 1080p on high setting per gpu check. https://www.gpucheck.com/en-usd/gpu/nvidia-geforce-rtx-2080/intel-core-i7-9700k-3-60ghz/high

Benchmark of COD Cold War, desktop 2080+i9-9900k, highest setting, 1080p is 102 fps on average, P1 = 71.8 fps (if I understand correctly 99% time fps is above 71.8).

if you turn on ray tracing, there is about 30% drop in performance, 65.7 fps on average, P1 = 48.

https://www.notebookcheck.net/Call-of-Duty-Black-Ops-Cold-War-Laptop-and-Desktop-Benchmarks.504420.0.html

9700k should perform very similarly to 9900k in gaming. 

Do you turn on ray tracing for this game?

Turning off ray tracing takes the "R" out of RTX 2080, that isthe signature feature introduced with that card.  But it's personal preference, go with what works best for you.

Yes, my ray tracing was on. Turned that off and it made a huge difference in performance, and I can't really tell the difference it made in game quality.