A/B switches are usually used for selecting one of two inputs to an amp, or for routing a guitar signal to one of two amps.

You can set up output A to send your guitar signal to the chorus pedal and then to the amp clean channel, and output B to your distortion pedal or the amp's distortion channel?

I need more info on what you have, and how you want to hook it up. If you only have one amp, or your amp only has one channel, you night want to look at a multi-FX box with presets, or a midi controller.