Re: Your files
LibreOffice is a good enough alternative for many but MS still is king as LibreOffice can't touch it for it's advanced features that lots of businesses rely on.
They certainly insist upon the features, but it remains an open question, in my mind, as to whether these businesses actually rely in these features, or they just think they do.
LibreOffice comes with one killer feature that MS never will, though, and that's that it won't ever stop working if it thinks (correctly or not) the subscription fee hasn't been paid recently enough, whether by glitch or by design, and it won't continually use your resources against your own interests, running license checks that do nothing but try to find a reason to stop performing the task for which the software (or the subscription for it) was purchased, and to harass you instead.
The makers of LibreOffice won't ever send audit teams to the place of business of their "partners" and try to find some technical violation of their Byzantine licensing schema so they can shake them down for penalties and still more future licensing fees.
LibreOffice doesn't push potentially productivity-breaking updates (since all updates have that potential) unless you want it to, on your schedule. It doesn't try to be some hip and trendy cloud service that doesn't really suit its purpose very well if you need to know it's going to work right when you need it to work.
Those are not advanced features by any means, but they're important ones, and it would take a hell of a list of "advanced" features that were of high importance to outweigh them, as I see it. The lack of these features alone is pretty close to being a deal-breaker in and of itself!