One thing that comes to mind is if you change the code-name of those email templates, it'll probably stop sending them :)
But to answer your question: many of the things that send emails, but not all, do have configurations. Settings / Configurations has "Registration requires email confirmation" - Store Configuration has settings for which ecommerce emails to send - For newsletters, if you don't set a Subscription Email Template on the newsletter, it won't send the emails.
For document edits, Settings / Content / Content Management has 'Send Workflow emails'
For registrations, if I recall the web-parts that you use to sign up for those tend to have checkboxes for 'send notifications'.
Customizing User Registration Emails
For groups, it's on the Group properties:
Working with Groups
But other than that, yeah, the simplest way is probably just changing the expected code-name so it can't find the template.