Id try to go for the unfiltered approach if possible. a FW system can be a little more forgiving of nitrogenous output of fishes, and in a two gallon Id say you'd be just fine with a standard plant load and a couple small fishes (or just one for really low maintenance)
In a two gallon you could also keep 4-6 danios and never see a spot of ammonia or nitrate if you have a few quick plants like hygro or val or hornwort (well-lit with established roots). the danio group would not need any additional surface area other than in-tank surfaces to process their collective wastes, but if you use larger fish or other kinds they may require assisted filtration in the long run. Both the filtered and non-filtered systems will work great, its just a matter of picking one and going with it.
This is not meant to contradict tracelynn's thread--its just my own average rambling. Actually I wrote down three of the Azoo items you've mentioned--- Azoo is my top favorite aquarium production company. They have food for every organism one could keep, as well as all the miniature pumps and light setups a nano reefer will ever need. its cool you like them too trace.