Advice for eGpu setup with 2016 15" Macbook Pro

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Hey Guys!
I have a 2016 15" Macbook Pro with the Radeon Pro 455 Gpu inside.
My plan is to get a working eGpu setup for both Windows and MacOs so I can play games in Windows and use the Gpu ins MacOs for productivity. I also want to just use an external Monitor, I don't need to get it to work on the internal Display.
I also already have a Nvidia GTX 970 from my current Desktop computer that I would like to use.

Unfortunately Razer doesn't sell the Razer Core in Germany but I found one on Ebay for 250€ which is a pretty good price considering that it costs double in America. Also I think this would be the only eGpu solution that I have access to at the moment.

Another thing is that I don't have massive amounts of knowledge to find solutions to problems which may occur during the process and money (the Macbook was already pretty expensive), so I would only do it if it really works well.

The guides from people who got setups like this to work always seem relatively straight forward to me but I wanted to get your opinion first before I buy something for 250€ and it doesn't work.

Thanks in advance!

Johannes