You realize that the 2015+ Nismo Z has the same sport calipers as . . . every other Z with sport calipers, right? The only difference is the color. Which does not affect clearance
Offset is not that primary issue. SPOKE DESIGN determines brake clearance. The two wheels with the same width and offset may have different clearance because of how the wheel is shaped. This has been discussed repeatedly
Additionally, every Z has the standard Nissan bolt pattern: 5 x 114.3
Why would you want to replicate the stock wheel fitment which is utterly hot garbage?
Since you are in Florida, I would highly recommend contacting KamiSpeed, a Florida vendor here who is a Rays Wheels distributor.
https://www.kamispeed.com/
The Gram Lights range is probably worth looking at - it's the the entry level range from Rays Engineering, roughly $400/wheel depending on whats in stock, what sort of color you want.
In particular,
Gram Lights 57CR, a fairly straightforward 5 spoke design:
https://www.rayswheels.co.jp/product...=en&wheel=57CR
or
Gram Lights 57DR, a simply 6 spoke design:
https://www.rayswheels.co.jp/product...=en&wheel=57DR
Both are readily stocked stateside by Rays distributor in the US (Mackin Industries)
Take note of the EXTENSIVE legend chart that shows what brakes each size will clear. Thats how you know Rays is legit - they are testing and putting that info out there. Shittier companies will not because they're . . . not Rays.
Front: 18x9.5 +22
Rear: 18x10.5 +12
This will clear everything. Brakes, fenders, etc. You can use 245/45 front and 285/40 rear and match OEM tire diameter
Word of warning - think about why you want to go down to an 18. It's gonna look like crap. the Z's wheel wells are enormous - thats why you should be going the opposite direction and looking for 19 or preferably 20's
18 inch wheels are used by track folks for cheaper and wider tire selection
Enkei and Work have 18 inch wheels but brake clearance is going to be a more indepth discussion as their spoke designs do not clear the brakes in all sizes.