Sounds like you are on a good path then, mate.
I agree with the route you are taking. It’s a great blend between price and performance. My only “last advice” would be to overspec the NAS a little, as it would suck having to replace it next year as your needs change.
Have fun with your project and feel free to reach out should you have any questions.
If you’re going to run the NAS as the media server, you need to go with Intel to get quicksync. This because any file not compatible with your clients will require transcoding and you want that done with hardware, not software. It’s a lot faster. I’m using Synology as the referance point. No idea what the Qnap lineup looks like.
If the NAS is only the file host, then I’d say get at least 4 bays so you have some room to grow and that the CPU is less relevant. Depending on your use case, RAM could be more relevant if you’re running loads of containers. I’d at least get one with an extra slot and/or non-soldered RAM, just in case. You most likely won’t ever need more than stock, but the option is nice. I’m running stock still.
I have the 923+ and have been very happy with it, but Jellyfin is migrated to a N100 NUC. The NAS runs the .arr-suite, qBittorrent, autobrr, Flaresolver, all in Portainer, and I’m installing two 4k cameras soon for Surveilance Station. It’s barely breaking a sweat.
Sorry for the long answer