Should not have any effect on Wi-Fi at all (Or any of the network connections) try rebooting your router.
If you are using the USB stick for multimedia make sure you turn on DLNA or you may find that your phone etc. may not find it and you will need to use 3rd party software (VLC Media Player is good) which will always be slower.
Speedtest.net is designed to test your internet connection not your Wi-Fi, which is normally significantly faster. (Unless you have cable or fttp which may have more speed than the 2.4 GHz band)
Yes there can be interference however these days with modern routers (The article you mentioned is about 8yrs old) it should be minimal, and as TP Link make quality products there should not be anything major. (There is very little USB2 stuff about these days so they have had plenty time to fix USB3 problems, (Plus USB4 is the new standard that is now starting to become available)
If none of the suggestions in the posts above work, try getting a short shielded USB3 extension cable and plug your USB stick into that.