I must admit, I have never used Office 365.  My employer only uses the traditional Office.

We had an issue recently with a contractor who couldn't use our corporate Word templates, it wasn't actually an issue - he could still work on the documents and when he sent them back they reformatted correctly as soon as I loaded them onto my PC. 

The very worst that will happen is that someone will have to cut and paste your words into their format.

The reason we all use pdfs so much is because a Word document written on one machine (or in one company) is very likely to like quite different in another. So I wouldn't worry about it too much - it's just life. And the main point is that it's the words you write that are important.

That said, if you do feel like getting into how the Styles function in Word works you will become a hero to your employers!!!

P.S. totally agree with Simon about Visio, it's wonderful, I use it for loads of things.