Your frame rate in the practice zone is going to higher then in game vs bots or people. You are also running with triple buffering on which will up your fps a bit at a cost of input lag. I personally suggest turning shadows on at least low and turning dynamic reflections, fog details and triple buffering off for your setup for looks and high fps.
For sure this plays a part. Not much you can do about the game but you can reinstall your gpu driver and use DDU to fully remove your old driver first. I also personally ran into issues with the 417.35 driver for pascal for overwatch (not the latest driver anymore) so it very well could be your driver.
Side note, it feels random to me, on a patch that I may have to tweak or deal with fps issues of some sort when a patch comes out. Sometimes i have no issues and other times game turns into a fps dropping stutter fest for w/e reason. Sometimes deleting the overwatch folder with the settings in it (from documents) helps but not always.
There are a ton of things you can list, I linked to my old list in this post which also has things you can try if you want to dig deeper. Here is the link to that post.