sleeper pc

Hey guys. What are your opinions on pcie riser cables? -anyone had performance/compatibility issues? -I have pcie4.0 mobo (x570-p) and will at some point get 4.0 nvme, can I disable pci-e 4.0 for the gpu slot ONLY? -any brands to avoid? Or are the cheap £15 ones ok? -are pcie gen 4.0 ones...

Doing a copper tubing custom loop build into a retro/sleeper style PC and trying to find a full copper CPU block to match my copper Heatkiller GPU block, but cannot find any anymore. EK used to make a full copper block which looks perfect for my build, but they stopped making it and no one...