Would you agree that the second most powerful houses are: Boltons, Crakehalls, Freys, Royces, Florents, Dondarrions, Yronwoods, Harlaws?

I think the Manderlys are more powerful than the Boltons.

Crakehalls? Maybe, it’s hard to tell, post-Rains of Castamere.

House Frey? Textually yes, although there should be other equally or more powerful houses in the Riverlands. given geography and history.

Florents? Not with 2,000 swords they’re not. The Hightowers are almost certainly the number two house in the Reach and are many times more powerful than the Florents.

Dondarrions? No. Even among the Marcher Lords, the Swanns and Carons are more powerful. 

Yronwoods, probably. 

Harlaws, seems so.