Do these mount at the factory rocker points?

Yes, these bolt directly to existing factory mounting locations. No drilling or welding required.

Will I need additional fasteners, or does everything come in the box?

The bars are included with their assembly. Check your vehicle's service manual for the correct bolt specifications and torque specs if you're replacing existing steps.

Can I paint over the matte black, or should I leave it as-is?

The matte finish is ready to use straight out of the box. If you want to paint it a different color, light scuffing with 320-grit or higher will help paint adhesion, but it's not required.