Owing to balanced electrical properties of graphene nanoribbon field effect transistors (GNRFETs) they a suitable next-generation devices for designing high performance circuits. However, as the fabrication for GNRFETs is at premature stage the performance of GNRFET device need to be explored with variation in its parameters. This article comprehensively analyses the impact of variations in GNRFET parameters on its threshold voltage, subthreshold swing and Ion/Ioff ratio. As an application example high performance PPN 12 T full adder is proposed using GNRFET device. The proposed full adder circuit shows dynamic power, propagation delay, and low power-delay product of 43.3 nW, 0.47 pS and 0.02 x 10-18 J, respectively using 0.7 V supply voltage. The performance of proposed full adder is compared with five previously proposed full adders using 16 nm GNRFET model in HSPICE simulation tool. Further, the impact of the GNRFET parameters on performance of proposed FA is investigated. A study of this nature is expected to improve performance of computing systems used in internet of things (IoT)-based infrastructure and health industry which demand for high performance next generation devices-based circuits.