New to eBikes - where to start?

Hey everyone!

So, I'm totally new to the eBike world, but I'm already hooked on the idea of building my own custom ride rather than buying off the shelf. I'm thinking of converting an old hardtail mountain bike I have lying around, mostly for commuting ~10 miles each way on paved roads and some light gravel paths. My main question for you seasoned builders is: where do I even begin with choosing a motor and battery kit? There are so many options out there (hub vs. mid-drive, different wattages, battery capacities) – what are the absolute must-knows or common pitfalls for a first-timer trying to piece together a reliable and fun commuter? Any advice on where to start researching components would be amazing!