If you like the American locos they will all work OK on the same layout and in the same country so long as the correct input voltage Plug Pack/ Transformer is used , there are many brands to choose from including Kato, Atlas, Bachmann, InterMountain, Lifelike/Walthers and more, the only problem you may find is coupler compatibility, I have found that Atlas Accumate couplers are not always compatible with Micro Trains, don't know about the Bachmann Knuckle couplers, If I were you I would stick to one brand when starting out it can save you a few problems.
It seems you are tempted by the Bachmann locos and that is OK, the range is cheap and cheerful and could be a good starting point, the latest Bachmann range are mostly DCC ready and have directional lights.
A very helpful magazine for those interested in American model railroads is Model Railroader, usually full of helpful tips and reviews of models.