Yeah that’s a perfectly good setup and very similar to the one I use. Personally I’d stick with truenas for my software in the NAS as its perfectly good for file shares.

For getting the shares mounted on your LXCs you’ll need to use the proxmox CLI to add your shares as mount points as I don’t think the UI let’s you do it from memory though thatay have changed as I’ve not poked that part of my setup for a while.