First of all, which drone do you have? At least one supplier of the Alientech Duo II (covertdrones.com) says that professional installation is required due to the extra difficulty.
Secondly, keep in mind that the amplification from the Alientech Duo II really only applies to transmit from the controller. Whatever active amplification they do to the received signal from the drone amplifies both the signal AND the noise ... the signal to noise ratio remains the same. You need solid signals going both ways, not just from the controller to the drone. I assume the Alientech Duo II uses directional antennas which improve signal to noise for BOTH transmitted and received signals, but so do those "cheap $5 ... $10 dollar ones you find on Amazon." Good antennas have some advantages over just an amp.
A simple Google search shows several reviews of the Alientech Duo II, including some links to previous threads here on MavicPilots.com.
Lastly, keep in mind that the video link you referenced above is pretty much an illegal flight for both line-of-sight and height above ground, at least in the U.S.