How did the various WW2 submarines compare to each other in terms of construction methods - use of welding, prefabrication etc?
Probably the most famous deviation from the norm was the German Type XXI. This was more a production prototype than a mature design, and the desperate Germans were hastily throwing together modules made in various locations. The quality of the finished submarine was therefore variable. The type is known for its breakthrough performance figures. It certainly deserves regard for that, but there were significant problems as well.