I have a light carbon road bike, and I find the drop bars to be very comfortable. When I bought the Lefty 3 I thought I'd also like the drop bar, but I ended up hating it.
For some reason on every ride my thumb and next to fingers would start to go numb after longer 50+ km rides. It would happen a lot sooner if I was riding on gravel (which is why I bought the bike).
I tried raising the bar, rotating the bar, installing a shorter stem, and moving the seat forward. Nothing worked.
Out of frustration I decided to take a gamble and go with a drop-to-flat-bar swap.
Just by accident, I came across an article by Alee Denham, a world cyclist who designed a touring handlebar. The bar looked to be just what I needed. It had a nice curve to take the pressure off my wrists and it had a pair of horns for a more aero ride.
I had my local bike shop do the conversion and asked them to double wrap the bar for added padding. I also installed a pair of Ergon EC1 grips.
The gamble payed off-no more finger numbness.
I find the handle bar to be very comfortable and I love the Ergon grips. I also really like the horns. Anytime I hit a flat section, or the wind comes up, I switch my hands to the horns to get more aero.
For me, my Lefty 3 is now just about the perfect ebike. I love riding this bike!
Here's a photo of the Denham handlebar: