Which Direction for Good Handling, Forgiving Z?

JARblue

Just get the Sport model unless you like the Nismo body kit. The suspension differences aren't enough to worry about. Frankly, the car is pretty fun out of the box. And the rabbit hole gets pretty deep. Better brake pads and fresh Motul RBF fluid are really all you need to get started.

Fortune Auto coilovers are popular, but there are a lot of options. You can do a full coilover in the rear or you can keep with the stock divorced setup with separate strut and spring. SPL suspension bits are by far the best - get all of them if you can afford it.
Common square setup is 18x10.5 +18 with 10mm spacers in the rear.
Grab a Hotchkis front sway. Leave the stock rear sway. Or you might even decide to remove the rear sway altogether.
Make sure you budget for a ZSpeed CMAK kit to replace the stock CSC which is prone to failure.
Sustained high RPM driving in warmer temps will likely necessitate a proper oil cooler (stock one is worthless when the coolant gets hot).

__________________

wheelspeed

Thanks for all that info! Sounds good.