I am going to have to respectfully disagree with several of the things said.
First, I would say that the Pintail is certainly a classic. It is essentially an Anas Acuta with soft chines. And...the Anas Acuta was largely based off the Greenland kayak brought back by whatever the guys name is from Greenland (can't remember his name and not going to look it up for this post). I want to say that was in the 50s...and the Anas Acuta then became pretty much the father of all modern kayaks.
Now that is not to say that the Pintail is not without tradeoffs...which I would not necessarily describe as quirks. Although I have to admit that the Anas and the Pintail are among two of the only Brit boats I have not owned, but I can't fit in them.
The issues described above about the Pintail are completely a function of its high degree of rocker and short water line. These cause it to track poorly and have a poor top end speed, but also give it the great characteristics that people love about the boat--its high degree of maneuverability and playfulness.
There are no free rides in boat design. It's all about tradeoffs.
So the Delphin and others probably track better than the Pintail, but are not going to be as maneuverable. Speed and tracking, maneuverabilty and playfulness.....pick two.
Classic designs: certainly the Nordkapp, Explorer, Romany, Pintail, Anas.
Newer designs I would describe as "innovative" and they differ from more classic designs. They may offer better performance, and may not. I don't know for sure. Again, there are tradeoffs. I can say I have paddled a Cetus, and found it to have a really neat combination of characteristics, and it was much different from more "classic" designs, but not sure if it is "better" It has its tradeoffs too from what i understand (in high winds and following seas where it supposedly does not track well).
Now...boats that are "quirky" perhaps are ones that appeal to asmaller population of folks. Most boats are designed to sell and therefore aimed at a broad population of people.
I would say that the boats that you describe as "quirky" are mostly hard chined boats. Now they are kind of quirky and do appeal to a smaller population of folks. They have a unique feel that some like and others don't. And, some would say, that the design of a hard chined boat is largely aimed after a traditional look and does not offer optimal performance.
I am not sure if that statement is true...but it might be. Most higher performance boats do not have super hard chines like the Foster boats, Greenlander Pro, Anas Acuta, Bahiya, etc.
I personally like hard chined boats and think they feel fun and cool to paddle, but am not convinced that they are superior in all conditions.
On the Bahiya...that boat never really caught on i think, and perhaps there is a reason for that. I owned one for a while and did like it, but it was quirky and i found it weathercocked a lot...and i am not going to own a boat that needs a skeg in the wind.
Last statement...you said that NDK boats are classic in that they have low initial stability. NDKs are certainly classic, but are far, from a boat that has low stability. Quite the opposite.