ive been using kodi (xbmc was better moniker) since google killed sagetv. i recall attempting plex, but it seemed to lack some open/extensibility (its been awhile).
i have a side project i want to make as a modular plugin generating a cable layout with original air orders and networks/channels… kodi seems most optimal, but ill admit its been a long while since i looked at plex.
so why plex over kodi?
Plex has a reverse proxying service and can do upnp for you so it works with dynamic IPs out of the box with no need for a domain or forwarding ports. It defaults to upnp and falls back to the Plex hosted reverse proxy which also uses a dynamically generated subdomain and gives you a free SSL cert. Granted I prefer to host my own reverse proxy anyway with my own domain (when I had a static IP I just forwarded a port and set up an A record) but out of the box Plex does make it much easier for a non technical user to hit the ground running.
If I were you, I would just use jellyfin and don't mess with Plex Jellyfin is opensource, doesn't collect any data, and just faster in my experience
I do use jellyfin, I run it side by side with Plex on the same Intel nuc with quick sync - both with the exact same media folders added - and I let my friends choose. I don't think a single one of them prefer jellyfin unfortunately.