Question: I have a central shared drive for my organization with departmental subfolders accessible by the staff based on AD. I setup SharePoint Online and uploaded files in the shared folder into the SharePoint. Staff Personal files are uploaded as well.

Do I still need to keep the Shared drive? If not please advice.

What should be the best architecture to ensure staff can access the central shared folder on SharePoint as well as their personal files incase the Internet connection is down?

Answer: 
You only need to install the latest cumulative update listed [here](https://docs.microsoft.com/en-us/officeupdates/sharepoint-updates).

Because the update is "cumulative", the latest update contain all the previous update. As at the moment, 16.0.5071.1000 (October 2020) is the latest patch available to SharePoint 2016.
You just need to install October 2020 update for SharePoint 2016.

Here's an article below about description of the security update for SharePoint enterprise server 2016: October 13, 2020. You could refer steps in the article to install update.

[SharePoint Server 2016 October 2020 update.](https://support.microsoft.com/en-us/help/4486677/security-update-for-sharepoint-server-2016-october-13-2020)