I haven`t tried Plex - is it pay?
Both. You can get the free version, or pay for Plex Pass that lets you do more things and adds bells/whistles, but if it's simple streaming the free version's good enough - you'll need the Plex Server app for your source computer and a Plex client for your end device. I have a smart Sony here in BsAs, and the Sony Store furnishes the Plex client to allow the TV to stream content from the server.
I'm now into Plex bigtime: built a home server, ripped 1000 CDs, loaded 300 movies. I regularly listen to music and watch movies here in BsAs, streamed from my 8000 km-distant server.
And my tango collection is much better than what most Argentines have. They come to my place to listen.