1) yes they are great beginner markers. If you plan on playing speedball though, look for an electronic piranha/spyder or an ion.
2) That is a tough question. I prefer the Dye Invision series, but others love proflex's.
Check this link out, it should help.
There is NO "Best" Mask
3) Compressed air is the best choice. It is cleaner, and more consistant. Not only that, but I think it doesnt age your marker as fast as CO2 can.