How far your video will reach is a constantly varying number, it will change greatly with disturbance from other radio signals (noise in the area), obstructions (trees, buildings and such) quality of receiver and antennas, and so on.
The higher the frequency, the shorter distance it will go, so video should fail (5.8 GHz) before Taranis (2.4 GHz).
I am a little confused, you seem to want to go long range, so you will likely lose your quad doing so. Longer range flights are inherently dangerous to losing your equipment. When you fly out the antenna is best placed to give you good signal if you stay clean line of sight (nothing but air between the 2 antenna, goggle and quad), but when you turn to come back the quad frame (carbon fiber) will block some of the signal and you may lose video.
Are you sure you understand the risks? Your questions do not sound like you have the experience or proven equipment to go long range, or even medium range. Please be careful to slowly test how far you can go, or you will surely lose your quad.
IMHO