A lot of different ideas thrown back and forth in this video, but many of them are quite interesting.
https://www.youtube.com/watch?v=IgKumd7TRN0
The idea that Snoke was once a Jedi that survived the purge makes a lot more sense to me than him being some ancient Sith, or just some random guy who trained himself.
Him having received his scars during the purge (or order 66) then having hidden in the unknown regions, where he would then have encountered the remnants of the Empire could be an interesting backstory, which also has the benefit of not being to hard to explain to the more casual viewer. This would also explain why he doesn’t affiliate himself with the Sith and has instead made is own Dark Jedi order.
I like a number of this guys’ videos. Mainly the one concerning Rey’s backstory
I also found another tidbit while watching TFA yesterday that might suggest that Rey got her mind wiped. Rey dreams of the island where Luke is just like Revan dreamt of the locations of the Star Forge.
As it pertains to the Supreme Leader the theory is sound but just about any theory concerning him can be considered sound because we know nothing about him. I personally think that Snoke was either an Inquisitor or Jedi. I also think that we’ll get some indication of who he is in Rebels.