It all depends on the kind os music u want to do, if u change the keys alot u will sound jazyy if just change it in the right timing you can sound wharever you want,
You cant forget that harmony is nothing whiout a melody... Harmony was created to make melodies richier so if you want to know wich chord you sould go , just think in the melody n try around...
That's why people study harmony in the piano, is not easy to do harm n melod in the guitar, try to use you voice....