Do these mount directly to the factory fog light holes, or do I need to drill?

These use factory mounting points — no drilling required. They bolt into the existing housings from the engine bay side.

Will the switch work with my existing vehicle wiring, or do I need a separate relay?

The kit comes with its own integrated switch and harness. Run power directly from the battery to the switch, then to the fog light grounds. Relay not required for this setup.

Can I install these without removing the bumper?

Access from the engine bay side is possible, but removing the bumper makes the job cleaner and faster. Most installs take 20–30 minutes either way.