In some lessons they are using a higher note as the root (I) and lower as the IV and V. In others, the lower note is the I and the IV and V are higher. How do you know which way to play it? If someone says 12 Bar Blues in D#, my instinct is to start at the 11th fret on the 6th string and use an E shaped chord, then going to an A shaped chord at the11th fret on the 5th for IV etc. But in the D# lesson she starts at the D# on the 6th fret of the 5th string, then uses the E string for the IV and V. So how do you know when to start higher and when to start lower?