For opening Word documents, I’d highly recommend OnlyOffice. Has outstanding compatibility with documents originally created in Microsoft Word, and it’s free on Flathub
Another alternative if you have an existing 365 subscription would be the online version of Word in your web browser.
If you’re heavily into the 365 ecosystem though, do note that things like Onedrive compatibility aren’t all the way there on linux, so you’d miss luxuries like right-clicking a file and getting a shareable link, or sending a file to someone directly from the file manager. For these you’ll need to drag-n-drop the file into onedrive, or into your email app to send them.
Things like opening PDFs, viewing various video formats etc, are built-in and work flawlessly on pretty much all Linux distros. Support for opening encrypted PDF files should be flawless too, haven’t had issues with these myself.
Would recommend Linux Mint, or Zorin OS, as both have a pretty similar look and feel when coming from Windows