From my experience, the 190/55 vs 190/50-stock, makes no difference. I've "experimented" with taller tire and/or 1 tooth down on the rear, to hope to not keep looking for 7th gear at "high"way speeds. The difference is minimal, and all I rcvd for my experimentation is the CODE 24/rear speed sensor failing,,,,twice. I have a thread, on my CODE 24 troubles, about year ago. So, from now on I'll stick to stock sizes of tires and sprockets. This is just my experience.
I have had great service from Shinko tires. My fave might be the 009 Ravens. I ridden them to the Tail, and all over the fun roads down there. I'm not the fastest beast on the Dragon, but I rarely get passed, and I burn off all chix strips. The Ravens perform and stick very well. I can get over 4k miles.
Last year I thought I'd try out the Mich Pilot Power for the a change on my ZX14R SE for out (nearly annual for 33 years)trip to The Dragon. Great tires, but they flop at very slow turns, like turning a corner from a stop. My XXs and my ZX14R SE only ever did this when the tires were worn, generally flattened in the center. Otherwise a great handling tire. I've also had good luck with other Shinkos, 010 Apex, 011 Verge, which used on my XXs over the 17 years of riding them. I have some brand new 005 Advance waiting for my trip back to the Dragon in Sept.
That's my .02, or a little more.