I have different services in my server (a cloud app, a streaming app, etc).
What I do know is that I create a user for each service, each one having their own home directory, but not possible to log in with it.
That allows me to set up cron command per user, instead of running them as root. It also allows me to do backup per service and have it stored in its own home directory (I know... I should not have my backups on the same disk, even on the same server, but I don't have the resources to buy another server to put my backups on).
Minus the backup thing, is it a good idea to create a new user for each service? Or should I put everything under www-data and that's it?