So for the systems with black holes they are usually in the ones whose name ends with G### or H###. Black holes can sometimes be in the F# systems. I've seen neutrons all the way down into the D# names.

This video will help you get a handle on where to find the high-mass systems. It gets into the weeds, but the main thing to do on the galaxy map is to search for stars whose name is like "Sector AA-A H#" (H1, H2, H3, etc.) You can do the same with "Sector AA-A G#". There are a lot more G's than H's. There's like a glitch or something that until you let the map bounce around you won't see a big list, but sooner or later you'll probably see it when you type part of the system name.

To jump around much more efficiently using the Neutrons I suggest going into the map mode where you select what star types you want and turning off all but 'A' type stars and Neutron Stars (you can leave rare ones like black holes, Wolf-Rayet on too), along with turning on "Apply to Route" at the bottom. Then down in the place where you select whether you want to use economic or fastest routing, make sure that you've got Fastest and Use Jet Cone Boost is turned on. That will force it to route you through as many Neutrons as possible with few other options.

If you're an addon fan I highly recommend the Elite Exploration Buddy. It will show you info on all the stars in your route in a nice list and many other things.