This does seem high for Malling Jewel. You can nip out the top growing tip if you want. Yes, these canes are the ones that will bear fruit next year. This is an early variety, and when fruited, you cut them down. Meantime next year, new growth will come through, these will fruit the year after.
Make sure they are tied in well to the wires, especially if your site is windy and the canes are exposed. I'd earth up around them to make sure the roots are covered, also fork the earth about 3 ft away from the canes to improve drainage.