As far as what happened, I think you got the gist of it. According to Wikipedia:
Evil Morty... used brain scans taken from Rick to create a path outside of the Central Finite Curve, a walled off portion of the multiverse where Rick is the smartest man alive and restricts the ones where he is not... Evil Morty successfully escapes and steps into a gold portal to an unknown destination.
A similar synopsis can be found on fandom:
President Morty uses his machine to tear open the Curve and launch himself through it in a small spaceship. Coming out on the other side, he sees the rest of the universe and smiles, opening a gold portal with an improved gun and stepping through it.
As for what the repercussions will be for the R&M universe, I believe we'll have to wait for future seasons to answer that question. Inside the Episode didn't really seem to offer any further insight. Nerdist tries to explain the finale, but like us they don't actually know what happens to Evil Morty:
The show could also explore what lies beyond the Central Finite Curve. Evil Morty is gone, and we might never see him again. But if we do, what is the multiverse like without Rick as its ultimate genius? What’s life like for a Morty totally free of his grandfather? If the show ever travels back to that beautiful universe on the other side, it will likely be totally different from what we’ve seen before.