Are there existing fog light cutouts, or do I need to fabricate them?

The bumper ships as a solid panel. If your car originally had fog lights, you'll need to carefully cut the openings to match your existing light buckets or desired placement before painting.

Will this fit if I have a front bumper sensor installed?

This bumper doesn't come pre-drilled for sensors. If you're running a sensor, plan to either relocate it or carefully drill and fit it to the new cover after installation.

Do I need to paint this before or after installing it on the car?

That's your call. Many builders paint it off the car for better coverage and easier masking, then bolt it on. Some install first and paint in place. Off-car painting is generally cleaner and faster.