Could you post a screenshot of your F3 screen? It has a few important bits of information there that can help figure out the issue.
Another thing that would be super helpful would be to upload a HWiNFO64 report containing sensors, as that will basically record the usage of both your CPU and GPU during the report, which can help narrow down a potential bottleneck.
If you're comfortable doing that, you can download the newest beta version here, extract the .zip somewhere, run HWiNFO64.exe, then once it pops up, hit the "Run" button (leave both the "Sensors-only" and "Summary-only" checkboxes unchecked, just hit the Run button), and wait for it to finish scanning your system.
Once it has, a summary should pop up along with a window in the background containing a tree structure of all your components. Close the summary, then click the Sensors button on the top, and a new window should pop up containing a bunch of data from sensors across your entire computer.
Once that sensors window pops up, click the cog icon on the bottom right, then find "Log all values for report (consumes memory)" on the mid-bottom left, check that, hit "OK", then move the sensors window down a bit so it's still on screen while still allowing you to hit the "Save Report" button in the main window (closing it will cause the report to not include any sensors, and minimising seems to minimise HWiNFO64 as a whole).
Once you've hit the "Save Report" button, select the "Text Logfile" export format, hit "Next", then immediately uncheck everything (can quickly do that by just unchecking the top-most "Computer" entry), and then only check the "Sensors" entry right at the bottom, and then hit "Finish" to save the report.
The report will be saved in the same folder the HWiNFO64.exe file is located, so at that point you could just upload that, or better yet, open it and drop the contents in Pastebin or something for easier access.