I use Nextcloud with Nginx Proxy Manager and just use NPM to handle the reverse proxy, nothing in Nextcloud other than adding the domain to the config so it’s trusted.
I use Plex instead of Jellyfin, but I stream it through NPM with no issues. I can’t speak to the tunnel though, I prefer a simple wireguard tunnel for anything external so I’ve never tried it.
Edit: unless that’s what you mean by tunnel, I was assuming you meant traefik or tailscale or one of the other solutions I see posted more often, but I think one or both of those use wireguard under the hood.