What are you talking about? Is this some '00s problems that were fixed long time ago and now you're repeating some myths ? I'm getting same (~300Mbit) speeds via nginx+ TLS as I get via SSH for just file download
It is indeed an old problem (small fixed size buffers) but it hasn't really been fixed, they only increased the buffer size. You'll only run into this on high bandwidth, high latency connections, e.g. between NYC and AMS - you'll be limited to about 300mbps with stock OpenSSH.
