For track use, Castrol SRF fluid and Pagid RS19 should be enough.
I don't intend to track this car, as it is my daily driver.
I actually experienced brake fade with my stock 996 GT3 brakes at two track days, the problem was related to cooling. On the 997 GT3 they opened holes on the spoiler lip, increased the rotor sizes, added bigger brake ducts, and shifted brake bias to the back.
I think this type of threads are better suited to the Track forum, given the larger number of experienced track drivers there.
Street driving won't show any weakness in the stock brake system. The stock brakes are ok for the street.
My experience with single piston brakes at the track (E36 M3 and S2000) is that it takes an extra effort to modulate them properly, and under/over braking becomes more common compared to multi-piston setups. Being able to modulate the brakes more efficiently will result in faster lap times.
03 Celica GTS
04 Hummer H2
07 Cayman S
08 BMW M3