Which logging functions/message boxes etc. to use when in kate ?

Hi,

I'm unclear which logging functions, message boxes etc. to use when in kate.
I'm aware of
- qDebug() when to use this ?
- qcDebug() - when to use this, and what logging categories to use ?
- utils::showMessage() - this appears in the output tab, right ? So it's more 
visible than qcDebug(). 
- KMessageBox - for what errors/warnings/info should I use that ?
- wasn't there something like passive popup ? Should I use it ? In which cases 
?

Thanks for some explanations :-)
Alex