Advice on mobile MS Office apps

[Jux]

If you have a full version of MS Office on your (Windows 10) laptop and you needed to able to access, save, edit Word documents on any and all of the following:

Kindle Fire (Android)
Ondo tablet (Windows 10)
and iPhone 5 (not sure which iOS though)

What would you use?

Oh and what would you use if you wanted to spend as little as possible on it? So your preferred app/s and the cheapest but best apps?

OK, it was easy once I had the actual devices in front of me. Except for the tablet using Windows 10. Really hard to find something which worked.