So the difference between fake subs and real subs is that fake subs are just people pulling stuff out of their asses?
Kinda but not completely.
The people that do them, RRR in this case, would read episode summaries (albeit very detailed ones) and use their knowledge of the language to do the rest. When you watch the episode, you're not missing anything major, the story beats and big moments were all presented just fine in the episodes that I saw, it's just that...you're not getting a word for word translation. Now, dude who does this isn't fluent in the language, but I believe he's said that he's been taking classes for about a year and a half or so when he started Zyuranger. Often times what the characters say and what the subtitles say carry the same meaning, but they aren't really translations of what's being said...stuff like "his strength is unbelievable!" compared to "this guy's stronger than anyone we've ever faced!" and so on. (and sometimes they are totally off, but no worse than the sort of flubs TV-Nihon made in their Zyuranger episodes)
Essentially they're...interactive episode summaries. If you want to use them, yeah, go for it, but just do so under the knowledge that what you're getting is really only giving you the general idea of an episode and not a full on translation.
Also, Kinasin, if you like watching older shows, I would recommend Liveman, it's recently been completed by Grown Ups in Spandex and they do a pretty awesome job.