You're welcome.
There is an EQ setting on the iPhone, but it is a global EQ setting for all songs which can't be customized, and you can't set a different EQ setting for each song. Even if you could set an EQ setting for each song on the iPhone, you can do the same with iTunes, so the time involved would be the same.
With iTunes, you can customize your EQ settings - not use the default Rock EQ setting for a particular rock song for example, and this is transferred to your iPhone with the song. Set the EQ setting on the iPhone to Off or Flat, and your customized EQ setting for a particular song and your EQ settings for all songs in iTunes is transferred to your iPhone with the song.
And when the EQ setting on the iPhone is set to Off or Flat, you use less battery consumption when playing music.