This is only relevant for debian users.
If you assume you can manage your instances with the usual systemctl commands like systemctl disable/enable tor@myinstance beware that they have no effect.
Note: systemctl start/stop works as expected.
This is important to know especially if you have multiple configurations and want to enable/disable some of them to avoid running them concurrently.
I don't know the reasoning behind that design decision but all your instances are enabled due to [1], you cannot use the well known systemctl disable command like systemctl disable tor@myinstance to disable a specific instance. If you want to disable them you can use the 'mask' command: systemctl mask tor@myinstance this is less convenient because this way you wont be able to run systemctl start tor@myinstance (on a masked unit) or move configuration files away (also less convenient than native disable/enable)
[1] https://gitweb.torproject.org/debian/tor.git/tree/debian/systemd/tor-generat...