When you convert a normal bike to an electric one, you have desired performance characteristics and aesthetic characteristics. The problem is that the various characteristics conflict with each other: range vs weight; appearance vs utility; power vs stealth; speed vs legal requirements; unavailability vs cost; etc.
The only person, who can decide on the correct balance. You can achieve more of the characteristics if you source parts specially, but then they're more expensive. You need a motor, a controller with a HID, a battery and some sensors. You can get them in a kit or source them individually.
My recommendations are a rear 250 rpm 48v geared cassette hub-motor or a 201 rpm 36v one; a 15A minimum KT controller with LCD4 for stealth otherwise LCD3 or LCD5, or 17A if you can find one; any 48v battery from Yose or Greenlance; any KT pedal sensor and any throttle.
If you don't want to spend time sourcing those parts to get the nicest conversion, you can get the 250w 48v Woosh kit with the big geared motor that's heavy, but will last a lifetime of commuting.
The Woosh 48v TSDZ8 kit is also powerful. Crank-motors are a bit less durable and wear the drive-train parts quicker, and they're a little less dependable than hub-motors, but they're very quick and easy to install. The only problem I've had is the chain coming off because of the single chain-ring and 9 gears alignment, but that's easily cured with a chainguide, either self-made or bought. I'm 100kg and use the less powerful 48vTSDZ2 quite a lot, but it's slower than a hub-motor because you have to change right down to first gear to go up steep hills. It lacks power by comparison. The TSDZ8 is more powerful than the TSDZ2. If I were to guess, I'd say the TSDZ2 is somewhere around 12A to 15A, and the TSDZ8 18A to 20A. The only problem with powerful crank-drives is that the chance of mashing your gears is higher, which could leave you stranded.