Nothing updates unless you do it, but then once the update is done you can optionally go through the commit log of each plugin and even revert back specific commits if you don't like what you see.
To me that's a much better model than "hi, I see you opened your code editor, let me auto-update these 10 plugins for you. Hopefully things work out for you!".
IMO the user (you) should be in total control over when things get updated. This goes for the editor itself and your OS too. Otherwise you have no idea what the state of your system will be the next day.
I'm not sure I would trust jetbrains - it's closed source and I don't know what data they're phoning home, or telemetry. With vim at least I have the possibility to audit. With a closed source product, it's way harder.