Sounds like an interesting venture - how far out have you gotten? I'm curious whether the wide-zoom map is that true close up, there are some clouds in that outer arm's tail for sure…
I try to avoid nebula and similar "tourist hotspots" as these locations are visited by almost everybody.
Currently I'm just 8.5 kly away from sol, bernards loop is about 7 kly behind me. Sadly most systems are now beyond the jump range of my DBX (not optimized for jump range).
The galaxy map is more or less accurate. The brighter parts of the spiral arms are the core zones, there are enough systems in the darker areas that are reachable without problems.
EDD is a blessing and curse. Watching a spot appear just where you were headed is a bit sad sometimes, but hey they might not have been thorough!
There are so many systems, no need to worry if somebody discovered a system in a region where you are planing to go too (unless it's a nebula in short range of sol - in that case everything is probably discovered).