I can answer the question about katakana being used for some Japanese words. Writing something all in katakana is sort of the equivalent to writing something in all-caps in English; it places extra emphasis on the word, as if it is being said loudly or with more force than normal. Character names are frequently written in katakana because they're not Japanese names; even made-up, nonsense names would fall into that category. Sometimes even Japanese names are written in katakana because it is considered to be more feminine.