The weight of an e-bike isn't an issue because of the motor. As has been mentioned if you put out the same power on a regular bike you will be slower, even if that bike is lighter.
The weight is a factor when climbing or accelerating. When cruising along on flat ground the weight doesn't make as much difference. Having ridden 1000s of miles on a 60 pound touring bike, I have experience with this.
If you are totally comfortable on your e-bike with flat bars, you can try to set up your Defy with a similar position so the top of the handlebar is where your flat bar is now. From there you can start using the hoods and the drops as much as you want. Drop bars come in many different shapes and sizes so you can swap them if need be.