Q: also, how do you make interesting bass lines while still outlining the harmonic structure of the song
A: that's something that anyone can learn naturally with experience. the key to learning what the bass can really do is try to be uninteresting for as long as you can, and make sure you do what's absolutely necessary, and then as you gain more experience and intuition it will become irresistible to blow the door straight into another dimension, and still be home at 5pm for dinner