A. I would say it is highly unlikely that Avast could fix any malware automatically.
This was typically related to viruses that would change a file, were most malware is completely malicious. So it I guess move on to the next option and then the finale option deletion.
I feel this could lead to a serious issue in regard to any possible false positive if it gets to deletion (and you wouldn't know about it, if something gets broken).
B. Too all intents the user is unlikely to know about it, other than something not working.
This old topic might help,
https://forum.avast.com/index.php?topic=304475.0 - but things could well have changed in that time frame.
This support page is a little later and may also help -
https://support.avast.com/en-gb/article/antivirus-shield-settings/#pc -
I don't use hardened mode as I do want to know if anything security related, so I have little practical experience of it.
Silent mode is essentially popup related, but may have additional impact, a long time ago there used to be some notifications in the system tray icon area (bottom right corner of the screen). Again that some time ago and as I don't use Silent Mode or Hardened mode I'm working partly from memory and time marches on relentlessly.