Questions: Designing a Spacecraft

[Afterskies]

I should preface this by saying I'm using the word "design" loosely. (My gallery will give you an idea of what I'm looking do to)

I'm looking to draw one; I want to make it look realistic, have realistic stats, and I'm trying to figure out how to go about making it look plausible/realistic. The real life craft I'm currently using for scaling is the Falcon 9. Unfortunately, aircraft and ships are more my specialty.

What kind of stats do I need to include? (To be more descriptive/credible)

How would I figure these out?

How do I figure out payload weight/maximum altitude?

Amount of fuel for a craft going to the Moon or Mars?

How relevant would the Saturn V be (for scaling/stat purposes) for a modern craft trying to go to the moon?

Also, I know that Asparagus-staging isn't 100% plausible, but just how implausible is it? Say I want to use the same generic, reusable rocket bodies and just want to get a larger load into space or I want to get a smaller one higher up, how terrible would it be to go with an Asparagus?