Space Geography

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Two questions:

1) There is (at least in spiral galaxies) some sort of plane you could
construe 'horizontally' through the spiral such that most systems would
be
close to that plane. Is there any sort of commonly accepted definition
of
such a plane and any sort of coordinates available wrt that plane that
would
locate systems? (Thinking of the Milky Way)

2) Similarly, within systems, most orbits follow some sort of plane. Is
there data that lists how far on/off the plane of those orbits are that
known planets are? (I'm thinking something that identifies how many
degrees
off that plane the orbital plane of a system world is)

Mostly I'm curious if
a) most systems are flat with eccentric planets being unusual (and what
% of
planets are thus slightly or highly unusual/eccentric)
b) same sort of question with systems relative to the plane of a galaxy
(obviously highly galaxy shape dependent)

This came up in the context of detection of ships. I'm assuming
detecting a
ship against 'dark space' is easier than against 'clutter'. So, a ship
sneaking into a system could try to use cover (from system bodies and
maybe
any asteroid belts?) or just from staying within the plane of a system
or
the plane of a galaxy to try to make picking it out versus the
background
harder. (Assuming some levels of stealth as a ship without any should be
identifiable even vs. background clutter)

Would that sort of approach help? Does background clutter matter?

-- 
Only solitary men know the full joys of friendship. Others have their
family; but to a solitary and an exile, his friends are everything.* 
*--
Willa Cather (1873 - 1947)Solitudinem fecerunt, pacem appelunt
-- Publius Cornelius Tacitus (from the book Agricola, attributed to a
speech
from Calgacus)