I LOVE flying boats and seaplanes. And that is a neat and lovely one. But...
I'm pretty sure the fastest large flying boat, and really I believe the undisputed 'queen' of this class of aircraft would be the large (124' wingspan) and impressive
Kawanishi H8K, which could make a reported 290 miles per hour, and was also very heavily armed with 5 x 20mm cannon plus 5 x 7.7 mgs. It had a range of 4,400 miles and could carry two torpedoes or 2000 lbs of bombs / depth charges ... and had ASV radar.
All the more impressive since it appeared (though perhaps not quite in the above form) in 1942. They did well as recon planes. However they didn't seem to cope well with Allied fighters, or sometimes bombers (SBDs and once a B-24 IIRC).
If the H8K is the 'queen' of this class, maybe the the six engined, slightly frightening German
Blohm & Voss BV 222 is the king. also quite impressive, being bigger (150 ft wingspan, 121ft length) and (arguably) even more heavily armed (3x 20mm and 5 x 13mm mg) and probably much better armored and protected, but not as fast (top speed 242 mph) or as long ranged. They only made a handful of them but they were quite tough, used as an armed transport over the Med these beasts fought off numerous attacks, and one of them seems to have shot down a PB4Y (B-24) in a magnificent duel of giants. B&V also made the even bigger (197' wingspan) BV 238 which would have had impressive armament and capabilities but wasn't produced in time to be actually used.
The slightly smaller but always impressive Short Sunderland was in the running, though not quite as potent as either of the above, however, they made a variant called the
Seaford (aka Sunderland Mk IV) which certainly
was, with an armament of 2 x 20mm, 6 x 12.7mm, and 2 x (fixed) .303 guns, a range of 3,100 miles, and a bomb capacity of (allegedly) almost 5,000 lbs. They only made 10 of these but they were formidable warlike flying boats.
The American PBY was smaller and not as capable as any of these, but due to ubiquity and a certain suitability to warfare it probably had the greatest effect on the war, inflicting many casualties on Axis shipping and submarines. The closest thing the Americans had to one of the big flying "battle boats" was the PB2Y-5 Coronado, but it lacked the speed or range of the others listed above. The gigantic (200' wingspan) Martin JRM Mars had impressive range of 4,900 miles and would have been in the running of the big ones above but it was barely in the war and only used as a transport.
I'd also give honorable mention to the Japanese H6K, predecessor to the H8K (and roughly equivalent to a PBY) and the German Dornier Do 24, also in a similar niche to the PBY, but a very elegant design used by both Axis and Allies during the war (for a variety of convoluted reasons) and continuing to have a long life post-war.
My favorite though just for weirdness alone is the incredible Saunders-Roe Princess, a kind of flying cruise ship, with a superb bizarre art-deco / mid century science fiction appearance. Sadly by the time it was finished a long development process we were well into the jet age and they gave up. Somewhere in an alternative universe people are traveling to tropical vacations in these though, I'm sure of it.