The best place to begin is by watching all the training videos and reading the manual..
The most efficient way to achieve a good result would be to hire a professional to consult with you on the best methods for the projection and give you a lesson in how to use the software. ( I am available
Then you need to think about content too.
You have not given enough information to get much advice on specifics.
Edge blending projectors is not an easy task, I assume that's what you mean by 'stitching together'.
Ultra short throw projectors are not best suited for edge blending due to the severe angle of reflection.
I don't know what your space is like other than 'two walls at different depths, think stairs' so I can't say whether using a camera for the mapping would help. You could possibly take photo's of the space and use them as an output guide to test your mapping plan in the advanced output.