This is one of two e-bikes I made this year with the Tong Sheng TZDS2 motor.
It’s 250W, pedal assist only, limited to just under 25kph (so 
legal) and the battery is about half a kWh. Other options are available. There is a hidden menu on the controller where you get to pick from some preset wheel sizes. I chose 650B (those are 650x38 Marathon Plus) and it over-reads at 25kph by about 4% compared to GPS in my tests.
It’s torque sensing, and very natural to use. You get about four levels of assistance. A couple of chainring options are available.
I’m using their rear rack option. You can slide the battery in and out and lock it, or charge it on the bike. It has a built-in rear light. There may be front light options available too. The rack’s decently made out of aluminium bar.
I’m running it into an Alfine 8s rear hub gear. You can also use it with derailleurs but I’m not sure how likely the chain is to fall off the single chainring.
Pros: very natural to ride, although it tends to favour a laid-back low cadence pedalling style. Users are reporting plenty of range and enough torque to get up hills in places like Bristol. The UI is very straightforward and easy to use. Because it’s a conversion kit you don’t need anything special on your frame but I did braze a plate between the chainstays instead of a chainstay bridge to bolt the motor (and also the kickstand) to instead of using the sketchy clamps both came with.
Cons: there’s a bit of drag in the motor so I don’t think you’d ever want to ride it with no assist. Perfect for a city bike but not for a more sporty bike with a “get me home when I’m tired” option. You also end up with a pretty wide “Q” (spacing between pedals). It doesn’t seem to like turning backwards making it sometimes tricky to wheel the bike backwards. The wiring is also fairly untidy (although you can probably do a neater job than I did). There’s a wire from the motor up to the controller on the handlebar, to a speed sensor on the chainstay, and up behind the seat-tube (at least that’s where I put it) to the battery.
Overall: I’m very pleased with it for this application, but for a more sporty style of bike I’d look into the Mahle system that Reynolds can supply as the most likely option (although I haven’t tried it).