We have one such video below which includes the transformation and an interview with the designers. The transformation is far more involved than Optimus' but it also has partsforming. It should be noted that while Optimus' designer used to be a Transformers designer at Hasbro, Bumblebee's designer was not. Still, it is very impressive to see the lego set go from car to robot form with such minimal partsforming.
There is no preorder, the set will simply be released July 4th for $89.99. It can be ordered on the Lego site then, which is a good option for more expensive sets since they often have gifts with purchase: https://www.lego.com/en-us/product/bumblebee-10338
