I think you mean Insurgence.
Gameplay: I think it has some of the best features of fangames, which include items that replace HMs and a secret base where you can EV train and level grind infinitely against an Audino trainer, difficulty modes, option of lighter or darker story, and the delta Pokemon (some of which have megas).
Characters/Story: I wouldn't say they're as detailed as Reborn or Rejuvenation's. There's not as much Gym Leader involvement as in Reborn or Rejuvenation where you frequently team up with them and learn their life story, but they're also not just badge dispensers and do have a few appearances outside their gyms. It's the same with the villains where they're not as deep as Reborn and Rejuvenation's, but you still do get to learn about their motives as the game goes on.