As far as drop bars versus flat bars riding position is concerned it is perfectly possible to build a drop bar IGH bike. I have two set up that way. One uses the Alfine hub and Jtek bar end shifter and the other has a SRAM P5 hub and a twist grip shifter mounted on the handlebar end using a Hubbub type adapter.

For the Nexus 8 and Alfine there is also now a combined drop bar brake lever and shifter available. A couple of makers are fitting it to drop bar Nexus/Alfine hub bikes.