can I have the two separate controllers linked to play two different sounds OR, alternately, can I have them controlling different sides of a split keyboard with different sounds on the bass and treble sides?
Yes. Individual Instrument channel strips can be assigned to a specific MIDI 'keyboard' input.
On top of this, I would like to be able to launch the prerecorded events with either the foot controller or keyboard AND possibly send a click track to the drummer (not a deal breaker if I can't).
You can use the Playback plugin to play pre-recorded audio files. You could also use this to provide a separate click for the drummer (using grouped Playbacks if necessary), or you could rely on the built-in Metroneome click. You should consider having an audio interface with more than 1 pair of outputs so that you can separate the clicktrcak frrom the other parts.
You will need to experiment to establish the best way for you to control all this with your Keyboard/pedalboard.