Take a look at following build thread. APS 6384 100kV motor was successful for following data :
You can certainly hit 20kmh+ just need higher pitch prop and / or higher voltage battery. If you are willing to spend hours on this you’ll be just fine. As of the battery, I would recommend something like @Flightjunkie did. I made a variant of this too
I’d get a 6384 motor with 120-130kV.
As for the battery, depends on what you are looking for. LiPo / Liion, etc
