Do these need any wiring work, or do they plug into existing harnesses?

These come with a switch assembly, so you'll need to run power and ground to the switch location on your dashboard. The fog light units themselves connect at the factory locations — test-fit before committing to wire routing and terminal connections.

Will these fit if my bumper cover is aftermarket or modified?

These mount at factory rocker points on the Accord chassis, so fitment depends on your bumper opening. If your fascia is stock or a direct OEM replacement, you're good. Custom or heavily modified bumpers may require trial fit before final install.

What bulbs do these use, and are they included?

The fog light assemblies are designed for standard replacement bulbs — confirm your bulb type and wattage by checking the unit directly or your owner's manual. Bulbs ship separately; you'll source those based on your preference (halogen, LED, etc.).