I think it was FerrtBomb who recently posted a fun analogy about meaning of most speed tests (bottom line, grossly optimistic, and not all that applicable to streaming). The issue with streaming is you need consistent throughput, ideally with consistent and low latency and jitter. General consumer SpeedTests don't tell you ANYTHING about these metrics.
unrelated, but in your logs you have audio devices at different sampling rates, which is never advise. Fixing is recommended
There are some reported known issues with nVidia noise suppression plug-in (RTX?) - I recommend disabling to see if plug-in in case you are using it and that is a problem source for you
What else is using your bandwidth? have you made sure NOTHING else is using that fiber connection? .. and I don't you you think that is the case, you need to know... as in monitor router utilization and any unexpected WiFi connection (presuming you have such).
There are more through methods to test upload throughput, but at a simplistic level, with a cleanly booted PC, all unnecessary background processes stopped, using Network Monitoring (Task Mgr or Resource Monitor) try uploading a large (1GB or larger) file to OneDrive, google drive, etc. Before the file transfer starts, is network utilization on the PC at/near zero? if not, wait until it is, or stop whatever is using the bandwidth. Now check at router level and confirm the same. Once you see nothing using upload bandwidth at PC level, and also nothign showing at router level, then start the file transfer, Does Ethernet bandwidth remain consistent? or does it drop off frequently/occasionally? if bandwidth isn't consistent, then time to check your router and/or ISP (most likely) assuming you haven't used some odd 'network optimization' techniques posted online that are the same as snake oil sales pitches from centuries past