VLC is the sort of software where if it can’t play it, I don’t know what else could. I guess I’d also try the ffmpeg command line tool to see if it can figure out what the video file even is, and maybe it could convert it to a regular format.
Also TBH such a video file would be interesting enough that you could probably post it here (if possible, or any metadata you can extract from it) and see if anyone knows how to play it.
Since Word documents are one of your bigger concerns, you can download LibreOffice on one of your current machines and try them out. That’s the same program you’d be using on Linux.
It’d have to be a pretty unusual video format to have issues. Similar to above, you can try VLC on Windows and see if there’s any issues.
Based on your description, I’d be surprised if you encountered any major issues. I’d recommend trying either Pop! OS if you’re OK with a slightly different UI from Windows, or Mint if you want something more comfortable. Note that you can create a LiveUSB stick of either of those, or any other distro. You can then boot your computer from it and take it for a spin to see if there’s any obvious issues.
The overall issue with global warming is not that one place gets super hot once and sets a record. Otherwise I could make news headlines by setting my house on fire and getting “hottest temperature ever! (at my house)”. Those local hotspots of fire will affect the average global temp only a tiny bit, because the earth is a big place and there’s lots of places not currently on fire. The thing to worry about is the reverse actually: because the earth is warming, fires are increasing everywhere, and then everybody will be next to a fire on that blessed record-setting day.