The continuous demand for smaller and more efficient electronic devices has led to the development of FinFET technology as a promising solution. In this study, we explore the potential of using Technology Computer-Aided Design (TCAD) tools to optimize the size and power efficiency of FinFET devices. Through careful design and simulation using TCAD, we investigate various strategies to reduce the size of FinFETs while maintaining or even improving their performance. We focus on the artful use of TCAD tools to analyze and optimize critical parameters such as fin width, height, and doping concentration. Voltage and temperature variations are combined to obtain an insight into their contributions. Results are useful to define the variability contributions in the early design steps and to select the most appropriate transistor sizing technique for a targeted application. Results provide a quantitative understanding of each contribution considering FinFET technology. Our results demonstrate the effectiveness of TCAD in guiding the design of FinFETs for enhanced power efficiency. The insights gained from TCAD simulations provide valuable guidance to work on advanced semiconductor devices. Through this work, we pave the way for further advancements in FinFET technology, enabling the development of smaller, more power-efficient electronic devices.