I would say that 90 F won't be a problem on an ebike, since you can rely a lot on the motor, and you have air flowing all around you. I mostly use a regular bike but then I just bring a spare t-shirt.

I would rather say that I don't like biking when it's below 35 F. Still doable, but not having to deal with that it should be really nice for you :)

Max allowed speed for ebikes on bikelanes varies but should be about 20 mph if you're using only the motor.