I don't quite get the logic behind the "Artist: Performer" formatting. Shouldn't it be handled like any other tag? Right now, you can't use <Performer> in a virtual tag, I just tried. Virtual tags with <Artist: Performer> don't work either.
<Artists: Performer> should be fine in a virtual tag, I've used it myself. Are you spelling it correctly (Artists is plural)? Although you'll probably still have the issue with multiple values: Virtual Tags just don't do multiple values.
The "Artist" field in MusicBee is not a 1-to-1 match to the actual Artist ID3 frame. It includes that frame, TXXX/Performer, a couple of different formats for Remixer, and TXXX/Guest Artist. Thus the need for the multiple artist splitter, so you can specifically designate which of those fields you want a particular artist value in, and also enter a Display Artist (another TXXX/ frame).
When you put "Artist" in the main panel, it shows the Display Artist if defined, else it will show all values in the different artist fields. In column browser, it shows the split values and ignores the display artist. The "Artists" field always shows all artist values, ignoring the display artist. "Artists: [whatever]" will show only the values in that specific frame (Artist, Performer, Guest Artist, or Remixer).
All of those fields should apply the Ignore Words setting, but that's moot right now since you can't put them in the column browser. I'm guessing you're thinking of working around it with a custom tag like $Sort(<Artists:Performer>)?