I certainly haven't noticed any daily windows updates.
Now I don't know if that is down to my settings, Windows Defender is off when you install Avast. But it still has an option to do periodic scans (I have that disabled also), I don't know if this is your source of daily windows updates.
Avast doesn't have daily program updates, it may check for emergency or regular program update availability, but that shouldn't take long, just to check. The Virus Definitions are updated daily (again this shouldn't take long) and there are also virus definition streaming updates which are very frequently, but they are usually measured in KBs not MBs.