In The Hobbit, the Dwarves' beards are described quite explicitly. The convoluted history of how Tolkien thought about Dwarf women and their facial hair over is not something I want to raise here, but I realised I don't know if Dwarf culture is a monolith as far as beard styling among males goes. The Longbeards/Durin's folk are somewhat self-explanatory, and this explains Thorin and Co. There's the passage that Dwarves never shave their own beards off. But I really don't know what else was written about the other Dwarven kingdoms and cultures. We get the Firebeards, but that is only about colouration.
I'm thinking that in principle, there could be beard fashions through time, and indeed cultural markers between the different kingdoms. Our imaginations may be somewhat coloured by adaptations and the general fantasy genre always giving Dwarves big long beards.
(I'm not sure I buy Kili's designer stubble in the Jackson Hobbit films, or Thorin's well-groomed look, but that's a separate issue.)
This is not meant to be fuel for the current debate, I'm really curious now that I think about it.