Will these work with my factory bulbs or do I need LED bulbs?

These are complete LED assemblies — bulbs are integrated into the housing. You're not swapping bulbs; you're replacing the entire headlight unit.

Do I need a load resistor or decoder for these to work without error codes?

The plug-and-play harness is engineered for direct connection. If your vehicle requires a load resistor due to its electrical system, one may be needed — test after install and add if codes appear.

Can these be painted or modified after I receive them?

The black housing is finished as-is. Painting over the lens will obstruct light output. The housing itself can be modified, but test-fit first to confirm clearance and alignment before making any changes.