Just look at it this way, If you have just a non legally biding ceremony, it won't qualify you for a CR-1 visa. The same way that if you have such a ceremony, it won't disqualify you for a K1. However as noted on the link that I provided, it is best to have the ceremony after having the K1 visa in hand because the consul will have to investigate if this ceremony was legally biding which would cause a delay on the whole process.