There is a brief article on Wikipedia, http://en.wikipedia.org/wiki/Maxixe_(dance)
that tells you more. The Maxixe is, as you said in 2/4 time, with the melody usually in semiquavers (16th notes). The chordal vamp at the start of Barrios' Maxixe is very typical for the style.
The terminology is confused - for example Ernesto Nazareth wrote Maxixes, but preferred to call them Tangos - his best known piece, Odeon, is a good example, . although they have nothing to do with what we today call tango. As the article says, Maxixe music is a subgenre of Choro, but the definition of Choro is also obscure, and brasilian music forums are full of arguments about what the name means.
In any event, it's highly enjoyable music!