I've not seen net.ipv4.tcp_notsent_lowat=16384 mentioned before. Its certainly a curious one given the default on Fedora is net.ipv4.tcp_notsent_lowat = 4294967295 so just slightly different.
I see it seems to be related to making http/2 work best https://blog.cloudflare.com/http-2-prioritization-with-nginx/ and it specifically mentions servers rather than clients. So not sure its necessary on the client side, though it does seem like it would reduce bufferbloat.
yep these are server side things.
Sender controls congestion window, and I should have stated that second optimisation is specifically suggested for http/2 but does work well with ftp as well and other protocols I tested.
Defaults tend to not be changed often as developers have to be absolutely sure they not going to break things for the masses.
