hi,
it's probably doable, but you'd have to use dual GPU mode (Master GPU to drive internal display and Slave GPU RTX 4000 for 3D app via passthrough on internal screen, and direct output on external screen via HDMI / DP).
not 100% sure about resistor mod though. I've got a 3060m in my AW18 and TDP is around 55W (instead of 80W) but performance is still pretty good. RTX3k on the other hand, has very low performance with 40W TDP as only memory throttles (core frq is unchanged)
s7100x does not have native LVDS/EDP outputs. But it works OK on R4 / R5. But on R3 you end up with blank screen and no POST.
It's great news that wx7100 works. It's actually the fastest card available working with the venerable R3 π
Not sure about rx 6600 though. Someone tested it here and did not work on any alienware (was from xvision IIRC)