First sentence - Good. Absolutely correct. I put a lot of effort into getting an 'official' ST map properly sized in our galaxy. I have it
HERE. I had to create two in-between maps, to get a scale I could work with on both, so its as accurate as it can get, without me creating a file size in the uber-gigabytes. Two days after I did that, I finally found ONE that was accurate like mine (although still showing the region a tad larger than I have). I've been doing fantasy maps for fun and professionally since 2000, so I am pretty good at using different maps to get very precise scales. Space is a little trickier, but as others have noted, our galaxy is (comparatively) pretty flat. Just thank the space gods we weren't born in a globular galaxy.
As for the second part... rubbish. One of the questions I used to get asked a LOT when I did maps for D&D is "why are there so few settlements?" The answer is simple, and applies to Scify maps as well - they DO NOT SHOW EVERYTHING. They only show a small sampling of 'interesting' places, either for an RPG, or some other type of franchise. No-one cares about all the tiny villages (or rural farm planets), so they aren't in the lore, and thus don't make it onto maps. And just as there are thousands of towns all over the place you don't see, there are thousands of systems you don't see. Vulcan is 'right next door' to Earth, and yet you can fit a boatload of unheard of worlds in 16.5 LY. ST maps - like every other 'galaxy map' (especially real ones) - contain far less than 1% of what is out there. I am actually shocked that IP's like Mass Effect include the whole galaxy - its certainly not needed. Thats just writers not being able to visualize the material they are working with. And don't even get me started on writers... I had a LOT more respect for them before I started working with them. LOL
P.S. - I joined this site because I found this thread, and I need a decent map of Delta Quadrant powers for my own project. I'll probably stick around - I've been watching Trek since TOS aired live. Cheers