This is more a Windows issue than a router issue. Here is how to get a Grade A.
Download the "Grade_A_Buffer_Bloat.spg" config file attached and remember where you saved it.
Download TCP Optimizer v4 (or whatever the latest version is)
https://www.speedguide.net/downloads.php
Install and run as Administrator. Make sure "Modify All Network Adaptors" is checked - middle left of the settings screen
Click File -> Import
Choose the .spg file (remember where you saved it?)
It will now show an Import option on the bottom left
Click Apply changes
A window will pop up showing all the changes it is about to make - they all can easily be reversed - check Create a backup and save it - any issues follow the same steps and choose the backup (but there won't be any issues).
Once complete, restart your PC and rerun the buffer bloat test.
Congrats on your A :)
Grade_A_Buffer_Bloat.spg