eBike technology explained

Hey everyone!

Been lurking for a bit and finally decided to jump in. I'm really keen to dive deeper into the tech behind custom eBike builds. Specifically, when you're building from scratch or converting a regular bike, what are some of the most overlooked or misunderstood aspects of integrating the motor, battery, and controller? I'm thinking about doing a custom hardtail build for some light trail riding and commuting, and want to make sure I'm not missing any crucial tech considerations beyond just wattage and amp-hours.

What are your experiences with getting all these components to play nicely together, especially for specific riding styles? Any "aha!" moments or common pitfalls to avoid?