I've only had experience with LibreOffice and it works quite well. The UI leaves a little to be desired, but you can tweak that a bit to make it look better. I know for the Linux version it saves by default in .odf. I am not sure if this is the same for Windows, but if it is you can change that in settings so it saves in .docx, xlsx, etc... by default. There is another one called FreeOffice that works/looks a lot like the current versions of MS office.
Another option to consider would be the web versions of MS office? I it doesn't have all the advanced features of the dedicated Office suite, however if all you need is the basic functions then you could also try using that instead. It will provide the best compatibility of all of these, it's free and from a security standpoint much better as it's all hosted in the cloud instead of on your computer.