1. AC110 is a good filter, ask anyone here. Two of those should do the trick but it all depends on how many fish you have in there. A lot of people like to diversify their filtration and have something like an AC110 and a canister filter on the same tank.
2. A canister filter is an external filter (like a Fluval 305) that ususally sits below the tank with an intake and an outflow tube going into the tank. A biowheel is a wheel with stiff fabric-like material that is turned by the flow of water. This material gets colonized by lots of beneficial bacteria because it is very high in oxygen. A bioweel can be built-in to an HOB (hang-on-back) filter like a Penguin filter or attached to the outflow of a canister, like the Magnum 350 Pro System or even used in a sump like the Tidepool sumps. Google any of these filters and you will find pictures that might give you a better understanding of the different types of filters.
Which filter is the best? Everyone has their preferences and filters that have worked well for them and it's often a combination of filters. The first thing to remember is that you really want two kinds of filtration. Mechanical and Biological. Some would also add chemical filtration but that is not usually neccesary. Mechanical filtration means not having cloudy water or bits floating around and is accomplished with sponges, pads, filter socks or even polishing pads. Bio-filtration takes care of the things you don't see, like ammonia and nitrites and is accomplished with sponges, bio-balls, biomax and a myriad of different bio-media. Many HOB filters like Whisper filters, use cartridges that have mechanical, bio- and chemical filtration built in. The most experienced aquarists I've talked to have big tanks and use a wet/dry for biological filtration and a canister for mechanical filtration. I think this could be applied to any sized tank over 20g. I could go on and on but you can probably find posts by people more experienced than me to answer your questions, this is just to get you started.
