In light of the fact that the chuliyot should be similar length (I think that’s the Rosh), does it make sense to tie the last GRA chuliya as 12 winds so that the knots are evenly spaced? It seems to me that 3 winds per chuliyah is just a minumum.

On the one hand you are correct that the Rosh likes even windings. On the other hand the 3 wrap requirement per chulya is NOT a minimum but a strict
definition (Rebbi in Men. 39a). The reason that you see so many more windings per knot in white tying is because there is no issue of a chulya. So in the Gra, each chulya is 3 wraps, either white or blue. The number of chulyot per double knotted area is a different issue.
– Mois Navon