I never saw that graphic with the naming convention. I kinda knew it after years of looking at them and working with them though. It starts to stand out after a while. I would wait for the DS9XX+ to upgrade if that is you desired model though. It should be due for an upgrade release in the near future. Looking at the specs for that one (DS920+) it does support hardware decoding. Also, while looking for other things I found
this article that covers a few points for you, like Docker Compose! Granted, it is for Plex, but it clearly walks though the process for using compose that can be applied to other things.
For the location, you could just put the NAS near your router. The ones I have a near silent. Not full silent, but pretty quiet. Granted, mine now live in the basement away from all of use, but even in Va Beach where it was in my utility room it was just near the router.
One time I did have to run a wire from a lower floor to an upper floor, I went up through a closet into another closet and tucked the cable between the baseboard and the tack strip of the carpet. This hid the cable and still got me networking where I needed it. I did it close to the door of the closet so you would have to stick your head in and look back at the door frame to see it. Not the most professional, but it worked very well!
As you get closer to where you are looking to buy something, feel free to ask questions from me. I'd be happy to help with what I can.
I will say though, you can buy a high end Synology NAS that is really running full server grade hardware and able to combine everything under one appliance. I lean away from that personally because compute power needs grow faster than I'm willing to buy storage. So a mid/high end NAS will last for YEARS to come where you might want to upgrade the compute server hardware more frequently.