I’m not sure which distro to recommend (Pop OS seems popular among other comments), I strongly recommend using XFCE (or maybe KDE) for the desktop environment for someone who’s only used Windows before. It should feel familiar enough to them compared to Gnome
I’m pretty sure you can’t run the offline MS office on a Linux computer, even with the recent breakthroughs in the wine/proton area.
While the online in-browser 365 worked fine for me, I’ve found it quite limited. LibreOffice has some compatibility issues documents going back and forth between it and Ms Office.
I usually don’t use any “* Office”, but when I must, one software that works quite well for me is OnlyOffice
I don’t game that much on pc anymore, but this reminded me of this post about Linux gamers providing good bug reports.