Kodi runs perfectly, so plex should also run. Be careful with the installed android version, some apps from the store may not run (anymore). Check the minix forum to see which android versions are supported.

The remote control supplied is absolutely poor. The alternative: Airmouse Neo A2 is, with a little getting used to, pretty good for media centres, surfing etc. but very modest and a bit cumbersome.

I also have the MINIX NEO A2 Lite AirMouse, which is much better than the one that came with it.

Yes, both work, but there are better options like magelan. I don't like the remote control, I have a Logitech with touchpad (e.g. k400) for all my boxes. Have fun and search in Youtube under plex and sky.

As for the remote control, I bought the Airmouse Lite. However, I found out that it is only needed if you don't have a universal remote control (in my case the Harmony One).
It is so-so as an Airmouse, but it is highly recommended as a regular remote control. The original remote control only operates what is necessary, especially in the area of system configuration, as it is really just a control pad.

I can't say anything about PLex or Sky in particular, but I can confirm that almost all programmes from the Playstore run perfectly. I can also confirm that KODI and XBMC run without any problems.