Hey buddy
yea 7 strings are confusing to alot of people but I've been playing those kinds of guitars for forever now

The sole purpose of the 7 string guitar is to acheive a lo tuning without having the guitar neck bend or go out of tune.
so basically its meant for B, A, or even F# and G tuning

I tune full step down which is Korn's and Divine Heresy Tuning

Recently my band is gonna try 3 songs in the Drop A tuning which is Suicide Silence's and Chimaira's(Pass out of existence album) tuning

It's badass :]
takes about a week to get use to

You can pratice different tunings as well as chords on it too