Sticking LED bulbs into the OEM halogen fog light reflectors. Do they suck? I mean, do they have the same glare / light spill issues that headlight reflectors have when you stick in an LED or HID bulb? Not sure if this is really an issue in the lower power fogs with diffused lens.

Are there any that work well (9145 type bulb)? Brighter is better, but without blinding oncoming traffic? I'm looking for something in the 4300 K - 4500 K range to match my HID projectors.

I see'em on ebay & Amazon anywhere from 30w - 80w, but not sure what to get.

 

The housings are for Incandescent type bulbs that use the reflector.
Most LEDs are straight forward projecting so don't use the reflector.
The only dispersion you would have is smaller area of the total lens.
So it depends on what the bulb design is, how it sets in the housing..
I commend you on taking into account the blinding of on coming traffic.
Many times light are slapped on the front just because they look cool without regard to this.
The user never has to look at them from behind the steering wheel while driving.
Just to mention something else while here, there is increasing use of high power LED light bars sold by some well known stores.
These are illegal to use lighted on public highways because they are un-focused, too high in light output and blind on coming traffic.
They are also supposed to be covered while driving on the highway.
Off road, you do what you want with them.
Good luck.