IPA is what you would truly want if you want to get extremely linguistically accurate. But, Kana does a perfect job in the transliteration of Japanese sounds. After all, it is the native syllabary. Be careful with styles of Romanization as some might be confusing if you don't know all the rules.
No, かな aren't really that accurate, 'specially if you want to transcribe actual Japanese, with all its elisions and devoicings and allophones and stuff. かな is even less useful than foh-net-ik spel-ing fer ing-lish...
"If you like your clause structure, you can keep your clause structure" Stable: Current: Legacy: