Override placement

[Noeck]

Hi,

am I right that there is no \with-block for scores?
Why do I write \score (not \new Score) but \new Staff?

Is that correct: overrides on Staff or Voice level go into a \with
block, overrides on score level go into the \layout block?
Why am I not allowed to use a context prefix there? Like
\layout { \override Staff.Clef.color = #red }

Is there a difference between:
  \new Staff \with { \override Clef.color = #red } { a }
and
  \new Staff { \override Staff.Clef.color = #red  a }

Thanks for clarification,
Joram