Does anyone know if the helmet with fit with other Dwarven beards like Gimli's or the ones from the Fantasy Era sets?

It should, considering how wide his helmet his, fit to all Dwarf beards.

Hi Goliath,

Dain's helmet does work with Gimli's beard, and while I don't have any of the Fantasy Era dwarves, the helmet angle is such that it should work with them as well. I hope this helps.

Thanks for the answers, guys.