> Is TB2's lower bandwidth a bottleneck that would keep you from using a really beefy eGPU for these purposes?
What limits you is the power input and cooling capabilities of your TB2 box. A 1080 has a 180W TDP (before O/C), so you need to feed it up to 180We and dissipate that much heat, a Titan X increases that to 250W. TFA went with a 1050 because it only has a 75W TDP, and that could be achieved with their enclosure (by swapping out the power brick, the "out of the box" version only handles 30W TDP).
After that, it's mostly a matter of feeding the GPU enough stuff to do, giving it a small number of expensive tasks will utilise the limited bandwidth better than the reverse, which is why the efficiency of eGPU (TB2, but also TB3) increases as you increase rendering quality and the like (compared to internal) e.g. you might get 70% of internal at low settings and 90% at high.
What limits you is the power input and cooling capabilities of your TB2 box. A 1080 has a 180W TDP (before O/C), so you need to feed it up to 180We and dissipate that much heat, a Titan X increases that to 250W. TFA went with a 1050 because it only has a 75W TDP, and that could be achieved with their enclosure (by swapping out the power brick, the "out of the box" version only handles 30W TDP).
After that, it's mostly a matter of feeding the GPU enough stuff to do, giving it a small number of expensive tasks will utilise the limited bandwidth better than the reverse, which is why the efficiency of eGPU (TB2, but also TB3) increases as you increase rendering quality and the like (compared to internal) e.g. you might get 70% of internal at low settings and 90% at high.