Does this bumper have fog light cutouts pre-drilled?

No — this bumper ships solid. You'll need to carefully mark and cut openings to match your fog light bezels during preparation before paint.

Will I need to modify my factory bumper beam or lower valance?

The cover bolts to existing frame mounts, so your factory beam stays in place. Check clearance between the new cover profile and your lower valance — minor fitment at mounting tabs may be needed depending on prior body work.

Can I install this before or after painting?

Install after paint. Taping around mounting points during primer and paint is easier than trying to mask around an already-mounted bumper. Once paint-ready, bolt it on last.