Using eGPU with Internal GPU + GPU Suggestions

I've been running into issues, such as running out of GPU memory and encoding errors while editing footage (6K H.265 and Prores444) I have a habit of buying GPUs, only to realize that the one that I bought isn't powerful enough or has the right features that I need.

I have a External GPU enclosure sitting around that I used with my laptop and I was wondering if there would be any improvement in Resolve Editing if I hooked it up to my PC in tandem with a GPU already hooked up to the motherboard.

Here's my current system

Intel i9 7980XE (18 Core)

64gb Ram

Internal GPU: RTX 2070 Super

eGPU (Thunderbolt 3): RTX 2060



My next question is, Would it be better to sell RTX 2060 and 2070 and buy 2 1080 TIs (Use one internal and 1 in egpu) or a RTX 3080 (assuming I can get ahold of one).

Since you are using a Nvidia GPU, did you set "GPU processing mode" to "CUDA"? If it is set to OpenCL then this could be your issue.