Do the factory fog lights fit without modifications?

Yes. This bumper is designed to accept OEM fog lights as an option. The cutout dimensions match factory specifications, so no hole enlargement or custom work is needed if you're running the stock lights.

Will I need to remove the lower valance to install this?

Removing the lower valance is recommended to access fastening points more easily, but the bumper itself does not require valance modification. Check alignment with the valance before final fastening.

Should I paint before or after installation?

Paint before installation. This protects seams and fastening points from corrosion and gives cleaner results when masking around mounted parts. Install once the finish is fully cured.