A better ISP or a better WiFi connection. Most of the time it is bandwidth related. Maybe let them manually select a lower quality stream.

You can share your plex library. So the person can stream from your files. Pretty easy to set up.

I prefer it since I can max out my connection so it is much faster. I can download a 10GB movie in a matter of minutes. Also much easier to integrate with sonarr and radarr imo. And you don’t have the hassle of having to need a good download/upload ratio.