There is no skirting the issue, northern Balmain is hilly and it has great buildings and views. But on an eBike or if you actually like hills it is generally quiet to ride around and signage for bikes is quite good. Drummoyne on the other hand is a popular place for the bike commuters but its probably only worth riding around the once. Head to the green path on this map but make sure you are heading north as the most interesting road is St George Cres and its one way.
Distance 15km+ because you will also ride around Iron Cove
Shared Path 50%
Busy Roads 5%
Below is the Google Map. Its the red path in North Balmain and the purple line is the fabulous Iron Cove ride