You really won't know if you'll have algae problems at 2 wpg until you get the lights set-up and have it running a few weeks. You just have to set it up and see. Every tank varies, you need to experiment - we can only give you a general idea of what might work.
First step is getting the lighting in...then give it time and you'll know if you need CO2 and other fertilizers.
Personally, I have a 10 gallon and 5 gallon both at 2 wpg and I did/do have algae issues. I now dose Flourish Excel daily, Flourish every other day and Flourish Nitrogen, Phosphorous, and Potassium every other day. It took me a couple of months to get my fertilizers balanced and now I am beating the algae. This is what worked for me, what works for your tank will be different.
A good step in getting serious about planted tanks, is to get a copy of your tap water report so you can see just what is going into your tank every time you fill it.