What's the difference between brioche feuilletee and croissant dough?
They are very similar, here is the difference according to The Bread Bible by Rose Levy Beranbaum:

Croissant and brioche have the same ingredients: flour, yeast, salt,
sugar, milk, and butter. There are only two significant differences:
croissant dough contains almost double the amount of butter and has
only milk as the liquid component, whereas the liquid for brioche
dough comes mostly from eggs, with only a little milk. The eggs in the
brioche dough give it an airy cake-like crumb, while the large amount
of butter in the croissant dough, and the way in which it is rolled
and layered into the dough, gives it its flaky crumb.