Would it make a difference to mix the paprika, cumin and salt into the oil then mix them with the kale?

A quick whisk avoids clumping. I would think this enable a more even distribution of whatever herbs and spices one might choose to use in this recipe. It's just that cumin and paprika would not be my first choices.

The spices would probably clump in the oil and result in an uneven distribution (not to mention unappetizing globs of spices). I'd keep the dry together (mix those if you like) and then sprinkle evenly around.

No difference, its still the same flavor profile and should yield the same results and less mess. Go for it and make your life easier!