Again, this means nothing for overall power.
No? Again, nothing in the games insinuate this. It just means they hid like the cowards they are.
Take heed that the Primordials in their conceptual form were also unable to do anything about toppling the Olympians, otherwise why would Gaia have to ask Kratos to take on the Fates himself, the Fates who are repeatedly stated to be untouchable by anyone save for Kratos himself? Even after Gaia got her body back she was getting shredded to Swiss Cheese by Poseidon and got gaped by Zeus with a single bolt. Hell, why stop there? The Great Evils literally affected the Primordials themselves, they themselves fell victim to their own madness and rage created by said Evils.
Nevermind the fact that Ascended Athena exists, who is repeatedly stated to be above everyone else, including the Evils, minus Hope.
As for Ymir? His Dream Realm is literally just his consciousness. Nobody save for the Giants can access it and it isn't even noteworthy in terms of feats at all.