Regarding the question "is worshipping idols only idolatry. or is it more than it..."
Anyone who denies the worship of false gods admits the entire Torah, all of the prophets, and everything that has been commanded to the prophets from Adam, the first man, until eternity. This is essential to all of the commandments.
The Rambam wrote: laws of star worship 2:5:
Thus, we learn that anyone who acknowledges a false god denies the entire Torah in its totality, all the works of the prophets, and everything that has been commanded to the prophets from Adam, [the first man,] until eternity, as [Numbers 15:23] continues: "...from the day God issued His commandments and afterward, for your future generations."
Conversely, anyone who denies the worship of false gods acknowledges the entire Torah in its totality, all the works of the prophets, and everything that has been commanded to the prophets from Adam, [the first man,] until eternity. This acknowledgment is fundamental to all of the mitzvot.
The Rambam continues:
Whoever accepts a false god as true, even when he does not actually worship it, disgraces and blasphemes God's glorious and awesome name. This applies both to one who worships false gods and to one who curses God's name [as is obvious from Numbers 15:30]: "If a person commits an act of idolatry highhandedly, whether he be a native-born Jew or a convert, he is blaspheming God."