There's a network and system activity monitoring tool called GlassWire[1] with good visualizations and intuitive reports. When it was first shown here couple of years ago [2], I was very impressed. I don't use Windows anymore but hopefully the tool's still as good and maintained well. Maybe you can run it for a few weeks to either convince yourself there's no mischief from the old firm, or take more targeted actions.
[1]: https://www.glasswire.com/
[2]: https://news.ycombinator.com/item?id=8222652