Apparently, - or perhaps 'allegedly' is more appropriate - there are two separate planets that are referred to as Apu.

First, Apu is said to be the name of the home planet of the beings Vlado Kapetanovic (AKA Vitko / Viktor Novic) encountered in Peru in 1960. The planet would be located 'outside the Milky Way Galaxy.' Its inhabitants look very human-like.

The Mission Rahma contacts also refer to a planet Apu, though this one purportedly circles Alpha Centauri. Its inhabitants are human in appearance, but with a length of 8 to 9 feet / 2.4 to 2.7 m, they are taller than your average human.

Astronomical Data

In both cases, not a lot of information is given. Kapetanovic's Apu is supposed to be 'outside the Milky Way Galaxy, while the Apu from the Mission Rahma contacts would be in orbit around Alpha Centauri. It is not specified which one of the different stars (A, B or C) that make up Alpha Centauri this would be.

Physical Appearance

The inhabitants of Apu that Kapetanovic encountered are indistinguishable from Earth humans (phenotype A1), though they look like they are of mixed race:

"The inhabitants of Apu were tall. By their stature one could not distinguish them from one Earth race or another. The only thing was that their shoulders sloped differently and their figure was well proportioned, but they also had other different racial characteristics that one could believe had been formed by a mix of all the folk of Earth. The form of their faces resembled that of Arabs; the eyes were similar to those of the Mongol race; the nose to those of the Nordics; the beard gave the impression of being of the Hindu type, and the color of their skin was a rosy white.
After these observations I came to the conclusion that the greater percentage of their features seemed similar to the Mongolian race."

More info: http://rune.galactic.to/apu1.html

The inhabitants of Apu in the Mission Rahma contacts also are human in appearance but are 2.4-2.7m / 8-9 foot tall. This, effectively, would put them in the 'giant' phenotype (A3). They have Nordic features, and thin, platinum white short hair.

Source: Juan José Benitez, OVNIS: SOS a la humanidad, in which he describes his investigation into the contacts of Carlos and Sixto Paz Wells.

Additional considerations

Both of these contact cases took place in Peru, where the term 'Apu' is well known. In Quechua, the word can have a number of meanings, including: authority, Lord, rich, mighty, supreme being, boss, supreme, casique (a sort of Andean major), chief, powerful, wealthy. The term is also commonly used to refer to kind of (male, white) mountain spirit.
Keeping in mind that all contacts with both 'Apu' civilizations took place in Peru, and that the term has a special meaning in Andean culture, the possibility exists that 'Apu' may be more of symbolic name, than an actual name. An alternative explanation, of course, is that somebody is not telling the truth: the Paz Wells brothers, Kapetanovic, and/or the aliens.