I know the DR/BDR and ABR are of course separate concepts and serve different functions, but in many cases is the ABR router for a given area also made to be the DR? Or would the DR be more often an internal router in an area? I'm guessing it doesn't necessarily matter, or that the latter is more true, but I haven't seen actual production network examples. I get that the DR is the sort of "leader" or main representative for the area its in, so that the other routers in the area are connected primarily to it and don't need to know the routes to every other router in the area, thus saving some overhead and processing. The Area Border Routers merely serve to summarize the routes from the other areas and advertise them into the others they're connected to... meaning to the DR of that area? Like is that what a Type 3 LSA is essentially?
Also, as a related question... what exactly is this "non-broadcast multi-access" network connection type that keeps getting mentioned in these contexts? It's not explained well in the books I've read for the cert.