Quicker update of smtp config than launcher rebuild?

Support Self-hosting
1

Is there a quicker procedure to update the smtp server details (just the smtp address for example) than running ./launcher rebuild app ?

2 
   ./launcher destroy app
   ./launcher start app

Works if you have just changed environment variables.

3

Does this also work for just altering database connection details? And does it work for any settings in app.yml other than the actual app itself?

UPDATE:
In minor testing the answer appears to be YES, this does work.