GT-R fluid is just a way for them to upcharge you. It's nothing other than a better fluid - it does not help the CMC or CSC issues other than helping to prevent the fluid from boiling. If you're upgrading, I would recommend Motul RBF600 - it's better fluid and not more expensive (locally, I find RBF600 cheaper than GT-R fluid).
The OEM pedal does allow for some adjustment. But it doesn't really do anything other than change the pedal travel length. The engagement doesn't change, and that stupid double-hinge spring action is exactly the same. There are two clutch switches - upper and lower. You can screw in or unscrew either or both switches to shorten or lengthen the pedal travel, respectively, but it doesn't do much. If you adjust the lower switch too far, the car may not start or it could possibly prevent the CMC from actuating fully. The upper switch is a cruise control switch that might prevent it from working if not properly adjusted.
I recommend one of the ZSpeed options when your CSC goes. And the RJM clutch pedal allows for a lot more adjustment and has a linear pedal. The entire stock clutch hydraulic system on the Z is $hitty and ideally should be replaced asap
