I have a number of Bachman locos. They don't run too well, but for $30 at a train show you just can't beat the price. I have had the best luck with the FT-A and FT-B. None of the hooded diesels run as smooth. With Bachman's lack of QC (I have two GP35s, bought at the same time, one runs slower and makes a lot more noise than the other), YMMV. If you can spare the $$$, then go for an Athearn RTR DCC ready (pop the shell off and PLUG in a decoder), or an Atlas. I have seen heard good things about Atlas. Most modern DCC decoders are dual-mode, so they run equally as well on DC or DCC. You do lose functions on DC, however.
As for DCC, it is NOT AC. It is swtiching bipolar square wave DC. It looks to a dumb loco (non equipped), or a light or whatnot like AC, but it switches something like 8000 times a second, is not a sine wave, and has both 0 and 1 bits, the zero bits being longer. When running an analog loco, it zero stretches, in order to create a positive voltage potential over time, and make a DC loco go forward. NOT RECOMMENDED.
A command station and a booster are TWO different things. The wall power goes into a power supply, the AC or DC output from that goes into both the command station and booster in parallel. The command station takes signals from the cabs, and makes a low current DCC signal. Then, attached boosters that that signal and amplify it, typically to 5 amps, although there are up to 10 amp boosters out there (for G gauge). That boosted singal goes to the rails. The confusion about a command station or booster probably is a result of the fact that most modern systems have the command station and the first booster in one box, with an internal connection. Then, extra boosters can be added. In the case of Digitrax, ever booster is a command station, but there is one model meant to be a command station and booster, and one meant to be a booster, but also features a command station that is diabled when running with another command station (you can have as many boosters as you want, but ONLY ONE command station). Digitrax, NCE, MRC, and LENZ have integrated boosters, wheras the 10 amp NCE system, and CVP have separate command stations and boosters.
Two great sites are wiringfordcc.com and the dcc wiki (google it).