The ones with two blue LEDs will look very blue over your tank---- those blues are a lot more powerful than you might expect.
They will grow plants just fine though. I've seen planted tanks with that exact same bulb over it (3w, 2b) and it looked nice. Definitely blue but the tank looked fine to me.
It should, you will most likely need multiple bulbs since their footprint is only about 12" in diameter.
As long as you are able to suspend the bulb up higher, you can get good PAR levels on these on probably more than a 12X12 area. For a low light area, you could probably get 20X20 roughly. If you have it low enough that it's only lighting a 12X12 would definitely be high light and require CO2. Reef guys use it low enough to get a 12X12 area and I've seen these hit over 200 micromols at that sort of height.