PC or Streaming Box

[CmdRiker]

Thank you guys, much appreciated, I really want to fully understand all the moving parts of this. 

So, LibreELEC is a light OS, Kodi is the "player" or "engine" ? Jellyfin is the "skin" or "GUI" to navigate the media from my NAS? LibreELEC essentially replaces the Unbuntu OS I have now right ?

Just trying to understand all the moving parts of a system like this. Which part are doing what? I think I understand the hardware part IE: the CPU and GPU have to pull the content ie: streams, from the NAS via the Network port, then "decode" the video data and send it to my Anthem AVM 90 through the RTX HDMI port so that it can "decode" the Audio stream (dolby 5.1, 7.1, Atmos, DTX etc)  and pass along the already decoded video stream to the television.. do I have this right ?

I thought Kodi was just like Jellyfin in terms of a pretty interface (GUI) to manage and interact with my content, or does it do more than that? is the Jellyfin add-on simply for the look and feel instead of the Kodi look and feel ?

LibreELEC would be the OS, the OS is designed around a single job of running Kodi so it has everything it needs for video playback and barely anything it doesn't; with that, the OS is tuned for video playback.
Kodi would be the player/skin/engine in total but Kodi does not know how to talk to the Jellyfin server so that is where the Jellyfin addon comes in to bridge the gap and allow Kodi to talk to jellyfin

 Thank you.:-) Ok so, Jellyfin add-on in Kodi allows Kodi to talk to the Jellyfin server on my Synology, got it !

In that scenario, who does the decoding of the file / stream (ie MKV) ? the Jellyfin add on ? Kodi ? my Intel CPU ? my Synology hardware ? And should I actually care ? as long as my TV shows a picture and my AVM90 is decoding Atmos.. 

Could I just install Jellyfin client, minus Kodi, and just run that to connect to the Jellyfin server on my NAS? what is the benefit of Kodi if all I want to do is watch movies, maybe my picture collection and that's about it ? I mean my first test was Jellyfin on Ubuntu and it did work, but I don't know if my TV is the bottle neck at this point but video and audio was..meh.. The Jellyfin "client" I ran on my Ubuntu machine was just a web browser connecting to the JF server on my NAS. Mabye I was not using the "full" thick JF  client ?

maybe I don't need to dig that deep LOL ? But I do like to understand fully how things work, have all the information availble so that I can make the best decision for my use case.