Hi there.
About Live Vs samples/MIDI...like mentioned above: will depend on the Budget.
About recording Techniques...is the same as any other music...just try to match the source with the signal chain you think will work the best in context.
The major difference with regular songwriting, is in the Form and the arrangement...that's where you create the spaces.
True about intelligibility...work the frequencies that may interfere with the message....and.....all singers are not crated equal!!