Harmonizing on Different String Pairs
The exact same sequence of diatonic thirds that you learnt previously will work for every major scale because every scale is built upon the same order of whole steps and half steps (WWHWWWH). The distance of the thirds will therefore always be the same.
Taking the scale onto string 3(G) and playing a third above on string 2(B) will give us the same intervals but the shapes on the fretboard will be different because of the tuning difference between these two strings.
The major third has the two notes in the same fret:
Whereas the minor third has the diagonal shape, with the minor third being one fret lower on string 2(B):