Ventilation is a huge theme with the best road bike helmets; however, e-bike helmets don't have the same demands.
On a warm day, you want to experience the highest volume of airflow, but with an e-bike, that logic is slightly suspended as you can use the bike’s pedal assistance to reduce workload and avoid heat build-up without sacrificing speed. You will still want some airflow through to keep your head fresh under the helmet though.
Most e-bike helmets choose to ventilate heat by radiation rather than airflow. This allows heat to escape out of the helmet without having large vents that let rain or too much cold air in.