Hi, welcome to the forum!
Testing it separately is a great idea. MusicBee has been getting a number of false positives from av software lately, but as long as you're getting your downloads via this site, they're safe.
Running WMP and MusicBee side by side is redundant, they're both music players and organizers. In fact, I would recommend turning off WMP in Windows settings. It has a history of mucking around with music files without being asked to.
In testing on the separate computer, I suggest also making a copy of some of your files to experiment with. That way you can try importing and organizing your files without worrying about messing up your main collection.
Here's a good place to start to answer some of your questions:
https://musicbee.fandom.com/wiki/Importing