Adult Student New to Microsoft Office 365 online

The web versions are not a full featured replacement for the desktop apps, probably never will be. Microsoft publishes detailed comparisons online, here's for example the Word one: https://support.microsoft.com/en-us/office/differences-between-using-a-document-in-the-browser-and-in-word-3e863ce3-e82c-4211-8f97-5b33c36c55f8

It will of course depend on which features you need, and for most "lightweight" scenarios you'll probably be fine. For questions on specific add-ins, best check with the vendor producing the add-in directly.