The Z07 variant of PSC2 is a truly aggressive tire. Everyone who have an eye can tell with 100% certainty that Z07 variant PSC2 has much more aggressive tread patterns than off-the-shelf PSC2. In other words, Chevy was willing to sacrifice the wet grip for the dry grip, at least. And Chevy might be willing to sacrifice the consistency over peak performance, since you don't need more than 5+ laps worth of consistency if you're just aiming for the best lap time on the Nordschleife or the magazine conducted track test.
How much stickier then? A lot of cars are using PSC2s as an OE tire nowadays but Z07 has 10% shorter 60-0mph stopping distance than those cars, which is completely dependent on the performance of the tire, not brake system.
However, it's not exactly a standard tire of Z06. Standard Z06 tire is PSS and sick variant of PSC2 comes with Z07 package. Same goes for AMG GT R. The standard AMG GT R tire is already PSC2 but that's something more like off-the-shelf PSC2. If you want to get a corvette variant PSC2, you need to choose that option, which is offered for no charge.
And I don't think Porsche uses corvette variants of PSC2. Porsche always have their own variant of PSC/PS so far and I don't think they have changed now. Also, GT2 RS did not wear corvette variant PSC2 on the official photos of any kind.