Very good topic. I have build two E bikes myself , both with Bafang hub motors.
First bike was build with bafang bbs02 motor and lipo battery. I do not recommend lipo batteries because they are like little explosives if you crash your bike. Motor and battery cost around 900 EUR and the kit was easy to install.
Now I have full-suspension bike with bafang bbshd 1000w motor and 0.8kwh Li-ion battery. Bbshd motor has amazing 160Nm torque which come in handy if you drive mostly off road. Building cost was around 1200 EUR.
I drive my bike every day, sometimes in snow and -25°C/-13°F weather, bike is always stored outdoors and still Bafang motors have always been reliable.
But no matter which bike and motor you have you will have great fun.