Do these bolt straight into my factory fog light openings?

Yes. These mount at the factory fog light points—no drilling or adapter brackets needed. Unplug the old housings and plug these in.

Will the smoked lens reduce light output too much?

Smoked lens does reduce raw light output slightly, but the full LED array compensates. You'll get better visibility than factory halogen units, just with less glare on wet roads.

Do these come with bulbs and wiring harnesses, or do I need to transfer parts from my old lights?

These are complete LED assemblies—bulbs are built in. You'll be transferring your existing harness connectors to the new housings. Wiring harnesses are not included.