For me, artist is always original artist. The track name is what I modify for remixes.
So, if I were to remix, say, Deadmau5's "Sofi Needs A Ladder (feat. Sofi)", then I would tag the final remix as
Artist: "Deadmau5"
Track Title: "Sofi Needs A Ladder (feat. Sofi) [Anorax Remix]"
I would try to make sure that the remixer's artist name is ALWAYS in brackets, whether or not the "feat. singer" uses parentheses or brackets
to reiterate:
Artist: Original Artist
Track Title: Original Full Title (Feat. Guest Performer) [Remixer's Remix]
As for remixes of remixes, I've seen them tagged in the Title as "[remixer 1]vs.[remixer 2][comma, semicolon or dash] Original track title"
so, in an example:
Title: Anorax vs 9bar - Kickstart
Artist: Example
the remix of a remix can get confusing though, I've seen it dozens of ways.
In the brony community, it get weird:
TeiThePony plots with Glaze - Avast Tei's Robotic Buttocks
Now obviously the title name has changed, but we're just weird that way