What prep work do these grilles need before install?

Sand the mounting surface and your grille edges lightly to ensure a clean bond. If you're applying a clear coat finish for UV protection, do that after final fitment and trimming. Carbon fiber benefits from a quality clear coat to maintain shine and resist fading.

Do these come with all the hardware I need to mount them?

The set includes the two grille sheets. Mounting hardware depends on your bumper's attachment points — measure your opening against the 47" × 15" dimensions and verify your mounting method (adhesive, fasteners, or clips) before ordering so you have everything ready for install day.

Are these safe to use as a functional grille, or are they mainly for looks?

The AF-2 mesh design allows airflow while protecting your radiator from debris. Carbon fiber's durability makes it suitable for daily driving, though mesh this open works best when your vehicle doesn't see heavy off-road or extreme weather use. In normal street or track conditions, they perform like any OEM grille insert.