Upgrades to Venture, and Word

It won't affect your Word documents.

Additionally I'm not aware of any issues with Word application 16.66.1 and Ventura

I subscribe to Microsoft 365 and update automatically but if you purchased Office instead, you can still update it. The current version of Word is 16.69.1 and I have no issues with it and Ventura. See the following for updates: https://learn.microsoft.com/en-us/officeupdates/update-history-office-for-mac

Upgrading your iMac to Ventura will not directly affect your Word documents. They will remain as they're currently formatted. You can access them if you have a version of Word that is compatible with Ventura.

You may have to upgrade to a newer version of the Word app. MS currently provides support for only the three newest macOS versions, and the Office and Word versions for Catalina may not work properly in the newer OS.