780ti + other incompatible card?

Hi guys.

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I currently have a 980ti which works on both my Hackintosh and Windows, but I'm after an upgrade. I know natively the highest you can go with nvidia is getting a 1080ti , but I'm not really after graphic performance on my hackintosh.

Would I be able to buy a 3080 for gaming on my Windows, sell my 980ti and get a 780ti to run on my hackintosh?

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If the 3080 isnt compatible with high sierra/whatever I upgrade to, surely it should automatically detect the 780ti?

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Also, I've never had dual GPU's, so how would that work with 3 monitors,which is my current setup?

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Thanks a lot!