Yes, I edit 3840×2160 Ultra HD from my GH4 – on my Dji Mavic Pro – I only recording 2.7 – because it’s only records UHD in 60Mbits !
In Davinci with playback problems – you can use:
Optimized Media
Proxy Mode
Render Cache
or convert to another codec
I do not have an overview of the cost price – think prices are lower in the US!
But what I paid for my Intel i7, 5960x cpu – I can now buy one:
AMD Ryzen Threadripper 1950X ProcessorSocket-TR4, 16-Core, 32-Thread, cpu!
You do not need 64GB RAM – 32GB is fine!