If 20% window tint was legal in my area, I definitely would have gotten it, but I had to go with 35%. In my opinion, 20% is the perfect level of tint for almost any car (except limos, large SUVs, and probably some other case-by-case vehicles). You also have to remember that tint usually looks darker on a black car, so if 20% is illegal where you live, you might want to get the next step lighter just so you don't have to worry about tickets, removing the old tint, and retinting it since that can get expensive.
As far as fog lights, I have Luminics JDM yellow bulbs in mine and I'm pretty happy with the color - plus, when they're off during the day, everything on the front of my car is colorless and I like that too (although, I do like the look of actual yellow fog lights on most cars). They're not terribly bright, but the yellow color is spot-on for my taste. I have a friend with an older BMW M3 and he took his fog light assemblies apart and sprayed the inside of the lenses yellow and they turned out pretty good, but I don't know if that's possible to do on a WRX. Lately, I've been pondering the idea of yellow HID fog lights, but I haven't looked to see if such a kit exists for the WRX.