e-GPU recommendation

Hi all,
I’m considering returning to wow after some time but instead of my old alienware laptop I now have a 7th gen Thinkpad X1 that has been covering all my work and personal needs so far. It currently can run the game just fine at low graphics settings, so no issues there as far as I can tell, however as I have been looking at the possibility of complementing my setup with an e-gpu I am curious as to where is the sweet spot for enjoying the game at high/ultra settings and frame rate, before seeing diminishing returns due to the apparent bottleneck limitations of an e-gpu TB connection and the demands of the game itself. For reference my laptop specs are:

10th gen core i7-10710U
16GB RAM

Many thanks for any tips and advice!