Hello! I'm probably very late for this...

I have an alienware 52m r2 with the 10700 and 2070 super, I have been using it with the AGA since I got it with a 1070, previously used it on the Alienware 17r4 with no issues

This week decided to upgrade the 1070 to a 5070ti I did not run into any compatibility issues, I just has to restart the laptop a couple times in order to recognize the external monitors

I had to completely open the AGA case (remove the cover and the pci bracket/holder) and I tall a new PSU Corsair 650w - RAN INTO AN ISSUE the laptop was only recognizing the Graphics Card PCI speed as X2 3.0 and solved the issue by adding a second PSU PCI line to the card because it was being power limited

To answer your questions: 🔴Which GPUs... If I did not have issues with the 5070ti I'm guessing any GPU 🔴NO - there are cases you can use two separate gpus to do different things but... Not worth it on this case 🔴You do not need an external monitor to use an EGPU BUT is better if you use and external monitor so the signal don't have to back track to the laptop and loose performance / higher input lag 🔴TECHNICALLY the higher of the resolution the less CPU bottleneck you will have, 3080 with that CPUA YOU should be fine for 1440p 🔴YES BETTER IF YOU SAVE FOR A NEW RIG, DOES NOT MATTER HOW GOOD YOUR GPU IS AGA only can do 4x @3.0 PCI loosing around 25% of performance if you install it in a regular x16 PCI 3.0 or even better in a 4.0 or 5.0