It says here that I have to choose if the project size is small or large, in plone's GSOC ideas 2023 list this project is mentioned as medium with 350 hours in time. Now, I am confused weather I choose small or large, as it clearly says mismatch of project size between Organization and contributor may even lead to rejection of proposal.
I think the ‘size’ on GSoC submission website refers to the project size in time. 350 hours is a large project, 175 hours is a medium project (https://developers.google.com/open-source/gsoc/faq#how_much_time_does_gsoc_participation_take). So for Refactor Class Components you would choose ‘large’ since Plone estimates 350 hours. The difficulty is additional information about the project good for you to know I guess.