Yup you can. In fact you likely should and will probably find yourself improving disk io dramatically compared to your original thoughts doing this. It's better in my opinion to let the hypervisor manage disks operations. That means in my opinion it should also share files with smb and NFS especially if you are already considering nas type operations.
Since proxmox supports zfs out of the box along with btrfs and even XFS you have a myriad of options. You combine that with cockpit and you have a nice management interface.
I went the zfs route because I'm familiar with it and I appreciate it's native sharing options built into the filesystem. It's cool to have the option to create a new dataset off the pool and directly pass it into a new lxc container.
I use using docker networks but that's me. They are created for every service and it's easy to target the gateway. Just make sure DNS is correct for your hostnames.
Lately I've been optimizing remote services for reverse proxy passthru. Did you know that it can break streams momentarily and make your proxy work a little harder if your host names don't match outside and in?
So in other words if you want full passthru of a tcp or udp stream to your server without the proxy breaking it then opening a new stream you would have to make sure the internal network and external network are using the same fqdn for the service you are targeting.
It actually can break passthru via sni if they don't use the same hostname and cause a slight delay. Kinda matters for things like streaming videos. Especially if you are using a reverse proxy and the service supports quic or http2.
So a reverse proxy entry that simply passes without breaking the stream and resending it might ook like...
Obviously you would need to get the http port working on jellyfin and have ipv6 working with internal DNS in this example.