This project aims to expand on existing research on the use of AI tools in writing education and L2 writing skill development. In current research on AI-aided L2 writing aspects like preexisting generative AI (GenAI) practices, perceptions and attitudes and their impacts on writing processes and outcomes are under-researched. What is more, the sustained interaction between GenAI-aided feedback engagement, motivation, affect and L2 writing development has been neglected. This project aims to expand on existing research on the use of generative AI (GenAI) tools in L2 writing process and feedback research by not only examining AI-driven pedagogical interventions and their effects but also by focusing on the initial GenAI habits of L2 learners. In a first step, the project provides insights into preexisting GenAI practices, perceptions and attitudes of L2 learners, thereby filling an important gap in current L2 writing research. The second study investigates these initial GenAI conditions within a single writing task by focusing on process-product variability from a cross-sectional mixed methods point of view. The third study intends to investigate L2 writing development, initial conditions, and interactions with individual difference variables, namely motivation, affect and engagement, throughout a writing course. This will be done by adopting an intensive longitudinal approach to investigate the individual development trajectories of L2 learners and the variability therein. The three studies will enhance the field’s current understanding of L2 writing and feedback processes and hold the potential to optimize L2 learning trajectories and outcomes.