I have 6 ports on my main server and I used to use them all just because I could, but I only really use 3 these days.
1x 10gbe for file server access, plex, downloaders, nextcloud etc.
1x 1gbe for DNS (Adguard Home), home automation stuff, web hosting, etc etc.
1x 1gbe for VMs
I could do them all with one 10gbe and split out subnets with Vlans in software, but I like dedicated connections where possible as it is easier to manage and monitor.
If you are looking to run a plex or jellyfin server it is usually best to use a dedicated player for those (nvidia shield, apple Tv, chromecast GTV etc…) as they always tend to have better support for things like multiple HDR formats and things like Atmos or DTSX compared to running a DIY HTPC box.