GT2 RS is the top track car Porsche makes on the 911 platform (other than the Cup options), using a more powerful Turbo S engine. The GT3 RS uses a slightly tuned GT3 engine, a naturally aspirated 4.0L flat-6, also a monster on any track, but slightly slower than a GT2 RS overall due to the horsepower deficit. The GT4 RS is the Cayman’s track-focused model, using a detuned GT3 engine, but in a mid-engined layout. All are track-focused cars. 992 is just a Porsche internal designation for generation of 911. In this case, 992 is the newest and currently on sale version of the 911.
GT2 RS is the top track car Porsche makes on the 911 platform (other than the Cup options), using a more powerful Turbo S engine. The GT3 RS uses a slightly tuned GT3 engine, a naturally aspirated 4.0L flat-6, also a monster on any track, but slightly slower than a GT2 RS overall due to the horsepower deficit. The GT4 RS is the Cayman’s track-focused model, using a detuned GT3 engine, but in a mid-engined layout. All are track-focused cars. 992 is just a Porsche internal designation for generation of 911. In this case, 992 is the newest and currently on sale version of the 911.