Ok, if those tanks are the ones that you plan of getting, those look to me like they are polypropylene tubes. I can tell because the tube material is "frosted" and not "clear" (polycarbonate). Yes, the endcaps are metal. I misunderstood what you were talking about before. Yes, those tanks are great. They actually are the first type of tanks that I got...I ended up having like 7 or 8 of them in either the 3.5ml or 6ml size. I got different colored tubes to help keep track of different flavors.
You will need a separate cartomizer and tank for each flavor of juice. The cartomizer will also need to be "punched", or have a hole in the metal tube of the cartomizer in order for the polyfill inside to feed the atomizer with juice from the tank. This means you either need to buy pre-punched cartomizers or punch them yourself with a $15 carto punch tool.
Another useful tool would be a tank accessory or tank filling tool, but it can probably wait until you are certain that you like using your first carto tank.