UV takes too long to really do anything to the air (like 5+ minutes depending on the volume of the space), unless you have some absurdly overpowered lighting going on. I'm guessing that you're finding suggestions to point at the evaporator coil to keep junk from growing on the coil (which gets wet thanks to condensation) and thus contaminating the air, rather than trying to kill any bacteria in the air.

>I'm also debating adding a layer of activated carbon to the intake filter.

You'd be better served buying a higher quality filter, perhaps one that already has activated carbon built in. Putting the carbon on yourself probably won't help as much as you'd hope as the carbon will clog up the pores it settles on and then the air that gets through will go through other pores, avoiding the carbon. Sure, it might help some, but a higher quality filter will help more.