1)
Why does it say "Goyim"?
1.
Radak #1: Even if all the nations would agree on one counsel, Hashem annuls it - "Kol ha'Goyim k'Ayin Negdo" (Yeshayah 40:17).
2.
Radak #2: Verse 12 says "Ashrei ha'Goy Asher Hashem Elokav"; other Goyim, the masses, attribute strength to other gods. A minority say that Hashem does not supervise or know man's deeds.
2)
Is the second half of the verse a repetition of the first?
1.
Radak: Yes, in different words, like verses often do.
2.
Malbim: No. Etzah is the desired end. Machshevos are the means that lead to the end. Hashem annuls their desired ends, and also their many thoughts and means to reach their goal.