In my android phone I have random downloading progress started by download manager. The notification says "play security information update". I have no idea if this is a regular android security check or this may be data leakage or kind of virus? Is there any document about play security? Is it a part of Google play protect service?
This is good.
Google Play Protect periodically scans your device to remove harmful applications.
As all other applications on your phone, it needs to be updated, thus the message on your screenshot.
This just update your app automatically even if your auto update is off and you don't want to update your app...because sometimes previous version are better and you don't want to update your app.This has nothing to do with security or scanning your app.It only works with WiFi and when your phone is charging...so if your WiFi is metered then it can finish all your data.