Mine is set to update on WiFi only. And everyday, without fail, the moment I plug my phone into a power source in the evening (could even be to my computer for debugging), it'll start going through and applying all available updates. The performance impact is always noticeable during the duration of the updates.
Other common case is when I pull into my driveway/office and happen to be charging my phone in the car and it gets into WiFi range. Boom, update everything time.
Google supposedly knows everything about my daily routine, and yet, somehow can't predict when I won't be using my phone. Even something super dumb like, screen off > 2 hours && battery > 80% && connected to wifi would make my autoupdate life much better.
Apple has the opposite problem. "Hey, your computer needs to restart, [Restart Now], [Remind me tomorrow]". [Remind me tomorrow] doesn't mean, oh I noticed that your computer went into sleep before tomorrow I'm going to restart it now. Thanks Apple, I had unsaved state open.
Ironically enough, Microsoft seems to have gotten the apply updates/restart frustration down. Maybe it's from all the flak they've gotten over the years.