In my former role as Web Producer I was also one of the SharePoint Online Coordinators for my department. With so many things in SharePoint Online not working with non-Microsoft products, I had a loaner laptop to help me develop the SharePoint Online features for our department, so I have been working on two systems for a while now.
With SharePoint Online and Office365, working with both systems is actually a pretty nice experience. You need to make sure you have Microsoft Office 2016 installed on your Mac. For Windows, it doesn’t matter if you have Office 2013 or 2016, but for the Mac it does.
If I have the files stored on SharePoint Online or in my OneDrive for Business, I can access them from either computer, and the online versions of Office, while missing some more advanced features, do a good job of letting me create and edit a file as needed.
And I love the fact that the file auto-saves while working online. No more losing changes because I forgot to save. Just remember – you still need to save your files in the desktop version of your Office suite.