I finally had the time & cash to setup my own media server. Hurray. Using the asus vivomini un68u (8th gen 25W Core i5u, HD620) - it's awesome and very powerful for it's tiny tiny size!
I tried both Plex and Emby running side by side running on top of W10.
Couldn't get headless hardware transcoding working properly with Plex+W10 (Tried everything, latest drivers, reinstall, HDMI dummy etc.). . Worked flawelessy with Emby on W10, didn't even need a HDMI dummy.
Kodi integration is far superior with Emby. If you use Kodi, Plex really isn't an option. There is no comparison.
Emby client for Android is better and have more options, such as aspect ratio (no zoom though =/ ).
Emby has better built in subtitle support. Had lots of problems with Plex and subtitles when transcoding. The subtitle add-on "Subzero" for Plex is awesome though and much better than anything available for Emby. I'm using a third party W10 app in order to fetch subtitles from addic7ed and subscene.
Plex is a bit bloated. I didn't care much for the News channel etc. Had to spend some time disabling/hiding that stuff.
I'll buy a lifetime emby license after giving it a few more months, but for my setup, Emby proved to be the far superior option. All in all both options are good and powerful depending on your needs and it's great to have a fallback option.
One thing that really surprised me is the lack of features in both Plex and Emby media clients (Android, IOS). Touch support is weak, very few/next to no customisation options for aspect ratio/zoom, pixel ratio, subtitle configuration, adjust audio delay, adjust subtitle delay and so forth. I expected that both the Emby and Plex media clients would have a video player comparable to MX video player or the likes. And this is why the Kodi integration with Emby is so great, because it gives you all those options. Touch support is still bad within Kodi itself though, but managable considering all the features.