I have two Proxmox hosts and two NASes. All are connected at 1Gbps.
The Proxmox hosts maintain the real network mounts - nfs in my case - for the NAS shares. Inside each CT that requires them, these are mapped to mount points with identical paths in each, eg. /storage/nas1 and /storage/nas2.
All my *arr (and downloader) CTs are configured to use the exact same paths.
It’s seamless. nzbget or deluge download to the same parent folders that my *arr CTs work with, which means atomic renames/moves are pretty much instant. The only real network traffic is from the download CTs to the NASes.
Edit: my downloader CTs download directly to the NAS paths - no intermediate disk at all.