OSMC-kodi version 18 is just around the corner, right now stable is still 17.6. If you want instructions on getting Netflix on your OSMC device i recommend this thread:
This guides you to install the latest nightly and then prepare for the netflix addon to be installed.
When you got Kodi 18 installed you got access to Retroplayer(still haven’t got support for all emulators RetrOSMC got), but i got GBA, NES, SNES, ScummVM and SEGA master/genesis running.
To install X-windows eviroment there is this thread:
Changeing windowmanager you have to figure out yourself, it comes with LXde.