I would say for sure sing in your own voice..not fake bluegrass, Scots, Carribean or whatever..sing their songs in your own voice. Straight as it comes out of your mouth...and no affectations based on pop singers of your generation etc.   And I on the other hand would beg you not to rewrite any ballads. If you enjoy writing songs, write them, in the style perhaps..but I would leave what has been around for hundreds of years unchanged..same as if I found an old teacup I would not be inspired to paint pretty new flowers on it. mg