Synchronisation takes place when something triggers it to happen. Typically when a database file is opened or closed is sufficient. Possibly also when a database is saved. If this database is on another computer or phone, and the database file is already open, then some manual action is needed on that device to resynchronise. There is no way to trigger it automatically, as far as I am aware, other than opening or closing it or manually triggering a sync.
Look at the menu item Syncronize. That should do exactly what you want https://keepass.info/help/v2/sync.html I would take a backup copy of both files first just in case....!
KeePass strength is its strong protection against hackers who steal your database file. It is designed to resist any attempt to breakthe password even with the world's most powerful computers. I have seen estmates of the time it might take to brute force break the password on previous forum posts but cannot recall the figures. I seem to remember that for a non trivial password it would take many centuries to break using the most powerful computers in the world.
Keepass already has an Autotype feature without any plugins - see https://keepass.info/help/base/autotype.html This however does not automatically fill in fields when a web page is opened and I am not sure it is even possible to write a such a plugin as that would require some integration with the browser. You normally initiate autotype by simply using the preconfigured key combination which then matches the webpage title (with wildcard matches) and then the autotype facility will then fill in the...
That is good news! Any thoughts about switching to a public cloud service for your Keepass master data file to give you the protection of offsite backup rather than a NAS as I suggested? The Keepass database encryption makes this safe and it is far more disaster proof than a local NAS. For historical reasons I actually use TeamDrive (Synqion in the USA for complicated legal reasons) which is an encrypted cloud service that can be safely shared via a shared folder but accessed by any local programs...
You would appear to have not yet found the description of "Triggers" https://keepass.info/help/v2/triggers.html#examples and https://keepass.info/help/kb/trigger_examples.html Where is all explained. There must be TWO separate databases. Your local copy that you open and update, and a "master" copy with a different name that gets updated automatically via the triggers whenever you update or open your local copy. The master copy can be on a local NAS or on any public cloud server. I actually recommend...
Virus scanners work by checking files against KOWN patterns. I have not checked but if it is a new version of KeePass you are using there is sometimes a delay in some AV packages updating their signature files which are used to check legitimate files. CLAM may not yet have been updated for a change in the Keepass program.
The published trigger solution synchronises the databases reliably and automatically once the triggers have been created. It has been working reliably for very many years. Why look for an alternative? It is relatively easy to set up the triggers if you follow the instructions on the web site and just works. See link above from Paul for the instructions link.