AFAIK, most of the 991's construction is not aluminum it's steel based with the exception of the front hood. Porsche uses a flat-6 not a V6, lower center of gravity on a F6 relative to most V6's. Rear engined cars have a relative advantage when accelerating vs FR and even MR cars due to the location of the engine aiding with traction.
Most of the performance gains on the recent Porsche's is thanks to the PDK and it's relative low gearing vs their 6 speed manual. Car and Driver tested a 987.2 Boxster S PDK with 310HP and got a 0-60 of 4.3, Road and Track got a 0-60 of 4.1 with the 987.2 S PDK.
The 991 C2S with street tires posts comparable lap times to the 997.1 GT-3 with their R-compound tires at the Ring. Nissan with their GT-R has really pushed Porsche to improve on their products.
By the time the NSX 2.0 come around maybe the 991 C2S will have about 420-425 HP based on how Porsche tunes their engines over the lifetime of their various models.
BTW: It has been long rumored that the 991 and the 981 will have a hybrid drivetrain sometime in the future.