The best feature of T-motor's U7 is the fact it has an adapter for conventional props, liberating us from the need to buy carbon-fibre types that are either cheap but have to be sourced from China, or previously imported by dealers who will be caning you.
Multicopters on this scale call for carbon-fibre because they firstly require substantial airframe stiffness so as not to disrupt the onboard flight controller (which I know to my cost) and secondly because they struggle for range and endurance and need every weight-saving measure possible regardless of the expense... another reason that they cost silly money.
A further reason for departing from propellers suited to commercial drones is that they are optimised for hover, which is what most of them spend much of the time doing; whereas the (air)boat we are building is more like a slow aeroplane with a pitch that is adapted to significant forward motion.
This is one reason for instance that the propeller recommend for this 280KV motor ~ 20x6" ~ is difficult to source, because it is too fine a pitch for a propeller of that size fitted to fixed-wing aircraft. The good news is that there is a multitude of propellers of 18" and below in a range of different materials and with a wide range of pitches.
Another reason to avoid propellers for conventional drones is that they come in pairs (clockwise and counter), whereas for cashflow reasons if nothing else we need only one, don't we? And if we do need a spare, it has to run run in the same direction, doesn't it?
It being Sunday morning in the UK, consider that as being the sermon... turning now if you would to your hymnbooks?
Nothing about invention is easy incidentally, and nor is RC as straightforward as it may appear. The U7 adapter provides for a metric 6mm drive-shaft but comes with a collet that allows fitment of a prop with a 5/16" (8mm) centre-hole. Large propellers may come with a 10mm centre-hole or else none at all... drill these yourself at your peril.
