A fan grille is just like a piece of trim. It's mostly for looks. Having said that, your CFM will vary with the size of the openings in the grille, and if you restrict flow too much, you may burn out the fan motor prematurely.
BTW, this is a public forum. We have private messaging for personal stuff. You'll just have to take a few seconds out of your busy schedule to check for posts every now and then.