wrote:
What would be the consequences of using whole eggs instead of simply
egg yolks in a cookie recipe, other ingredients remaining the same?

Both the yolks and the white will act as a binder, with the yolk also
adding a bit of fat.
If you use both, decrease the liquid in the recipe by one tablespoon.
The cookies will be a little lighter and fluffier, and the white will
cause them to burn very easily.
If you do use a whole egg, Beat the egg lightly.

Regards
Lee