How you plan to use your e-bike may leave you little choice on the class you select. For example, I live near the Torrey C. Brown Rail Trail where I put as many miles riding on the trail as I do on the road. Since the only class allowed on the trail is a Class 1, my only choice in is a class 1 if I want to continue using the trail.
On the other hand, if I used my e-bike as a commuter where assistance up 28 mph would help me ride safely in traffic, and I wasn’t concerned with traveling longest distances on a single charge, a class 3 bike would be my only choice.
Finally, if you want a bike that doesn’t need to be pedalled, a Class 2 bike is the only one that would fill the bill.