@kite722 I'm a manga only reader, which is a bad thing if you wanted spoilers but a good thing if you only wanted clarification. As far as I understand it, the approximate power standings should be something like (in order, with big gaps between each tier):
Tier 1: Milim, Veldora (the new demon lord introduced this chapter is apparently on milim's level, and we can assume veldora's sister is on the same level as Veldora)
Tier 2: Rimuru, Hinata, Diablo, Karion (not sure where Hinata is exactly but I'm guessing it's somewhere around there; Leon might also be in that area but I really have no clue)
Tier 3: most of the weaker demon lords (Frey, clayman, ramiris, maybe others), the ogres (benimaru, hakurou, souei, Shion probably in that order)
Tier 4: people like Gazel, the sorcerer's nation head, that mage that Diablo beat up
Tier 5: people like the beastketeers, clown troupe, etc.
I'd imagine that the ogres were high tier 5 before, and Rimuru was low tier 3 before, so the harvest festival raised Rimuru and those tied to him about a tier and a half in power.
That's my impression based purely on the manga; don't correct me with LN/WN spoilers, but if you have different impressions/corrections based on the manga then I'd be glad to hear them.