Hello Andy,
With Thunderbolt it should work effectively, however, I suggest to double-check the list of supported GPUs for this Amplifier in advance. RTX3080 is quite big and may not fit the box physically.
But with anything starting from GeForce GTX 900 series you should gain the additional boost in Metashape.
Although we have not tested Alienware Amplifier, we had some experience with dock-stations from other manufacturers and it worked as expected both with AMD and NVIDIA cards connected to a laptop via Thunderbolt. But the model that I have by the hand isn't big enough for GeForce RTX 3080 or Radeon RX 6800 XT, for example. That's why I'm suggesting to check the list of confirmed supported GPUs.