It’s easy to set up the basics but, there is a learning curve you'll need to patiently work through. I've also set up Plex (first time!) and am experiencing some quirks, but no deal breakers.
I can access the NAS from ‘away from home’ as well.
First thing I did was upgrade the RAM to 6Gb – standard RAM is fine. You do not need ‘expensive Synology RAM’ for the DS220+. I purchased “Crucial 4GB (1x4GB) DDR4 SODIMM 2666MHz CL19 Single Stick Notebook Laptop Memory RAM” via Amazon.
Best thing to do is join a few forums –
Synology:
https://community.synology.com/enu
Plex:
https://forums.plex.tv/
Also, YouTube is your friend –
The YouTube NASCompares site is also a great resource:
https://www.youtube.com/@nascompares
And, here’s a good basic setup video on YouTube: