If it is green cut back needs sealed, if it is been drying a couple of months then it probably wont need sealed.
White oak will make a bow in about 60 days if everything is done right but it will take a lot of set usually. There is a difference between dry and seasoned.
White oak can take some grain run out, but you can not just ignore the grain.
Rough out your bow, leave limbs 3/4+ thick or more. Too thin and they will twist. You can lash it to a straight 2x4 that will help it keep from twisting.
White oak is wonderful and a very overlooked bow wood.