codecs for video playback that you might need, will be downloaded and installed by the program itself. Nothing to do on your end. You don't need any codecs/pluggins for audio (unless you wanted to add specific VSTs yourself).
Concerning the UI .. yes you can set it up so that even a child can do it -- there is even a "party mode" to prevent drunken fools messing with your stuff.
However, this is a very powerful and complete program ... as such it is NOT plug and play to
set it up for children or computer illiterate adults to use. It has a bunch of options to fine tune playback for lossless music to very complicated systems, network playback on multiple clients if desired, a complete and customizable database for your collection. Consequently, the more you want it to do, the more time you will need to learn the software. So, no it is not what I call plug and play. The trial is free for 30days and full featured, don't buy it until you try it (you get to try for 30 days, no refunds once you buy!).
If you need it to be networked, you have to have set-up a network, if you need to access your collection externally you need to know how to get into your router. etc. If you just want to play your local music coming off of a 4tb hard connecting to a DAC or running from an internal soundcard connected to your stereo. Reading the links listed on the page I listed above say 20 minutes +30 minutes more for a basic configuration, and you should be up and running. (importing is 10x faster than itunes at least - will depend on the speed of your processor). Understanding every feature, could take you years
(but enjoyable ones!). Once you discover all the cool things you can do with a decent size collection, you might get hooked and become a power-user, spending hours customizing stuff, who knows
JRiver, like any good player, uses metadata (embedded tags) as the basis for its "Views" -- all of which are customizable. So the way you name your files is not important actually (if they are tagged). However there are a lot of reason to have your media file names and path names in a standard manner as you have done. Having Album Artist, Album, Track #, Track name, track artist allows you to recover all key tags in case of some disaster. There will be no issues importing your tagging. (personally I put the track number first, but JRiver can change tha for you automatically if you want to -- for playback in JRiver won't matter; for playback from Windows explorer on other peoples machines it might.