if you use the /projects/{id}/members endpoint, you may want to take note of this post: https://forum.inaturalist.org/t/api-projects-id-members-doesnt-list-all-members/16022/3.
that said, there already is a web page created by @kildor which will get project members: https://kildor.name/inat/members. more tools made by kildor are noted here: https://forum.inaturalist.org/t/several-external-tools-for-inat-data-by-kildor/19906.