Like all projects, you should think about needs, budget, and time. You’ve got a good list of what you want to run which is a good start. Budget is next, particularly considering the price of hardware these days.

FWIW, I run Jellyfin, Navidrome, the entire arr stack, Forgejo, Paperless, mealio, and Immich on a NAS with 24GB RAM and have never needed more. 8GB would have been a bit tight but probably doable. 16 will be plenty for you.