Welcome, @Molly_Henry, and thanks, @Emily_Roman for the good answer and invitation to reply.
All those links are great ones to follow-up on.
For the new member checklist, the use of a project template may be the right way to go, but I wouldn’t yet rule out the use of a task template for that purpose. Perhaps the checklist as a task template but an ongoing project for each client, either based off a project template if they’re all similar or not, is a thought.
More generally, I address some of these questions here if you’re interested:
Larry