Best tool I found for comparison of speed of TCP stack is TCPSpeed.

But it says nothing about speed of browser download. For this I suggest to install Apache / NGINX / MS IIS on local LAN and test download. Also many home routers can serve as web server.
Measure speed through internet providers gives you "real" numbers which are inaccurate due to the transmission route. Of course, measuring through provider is better than no measuring, but you have to keep in mind, that there are many other influences than browser.

[ Edited by sailor 14.08.2023 - 21:31 ]