External GPU compatibility with default GPU

URGENT NEED! hi I have MSI Raider GE78 HX 13V laptop with 1 Thunderbolt 4.0 port support and I want add eGPU. As default there is Nvidia GeForce 4080 Graphic Card but I want add external GPU of NVidia RTX A6000. one has got memory type as GDDR6X another is GDDR6 memory type. is that suit use both of them in order to accelerate Machine Learning tasks ? those both are compatible to use them at the same time ?
also another question the Cuda support of RTX A6000 ? in GeForce I can handle CUDA but I wonder for RTX A6000 has got specific Cuda support.
and another question; what details should I pay attention to in order to run both of them seamlessly? do I skip any details ?
and last question; May I add external GPUs more than 1 into 1 GPU Dock Station and connect them 1 Thunderbolt 4.0 Port
my OS : Windows11.
I need answer swiftly please someone inform me if has got knowledge