Might want to start here. You might want to see if the pipes can be sourced from Aliexpress, in case your supplies will cost a lot more than the project. As per your cooling ambitions, mind sharing your entire project/build log with us? Perhaps your project can be streamlined...?
My system was previously water cooled with a Vega Frontier Edition. I switched the Vega for an RTX 3090 and got around to adding a water block to it. But when I switched to an RTX 3090 initially there were no waterblocks. So I did a quick and dirty loop with flex tubing for my cpu.
I am using an inWin 905. Msi x370 titanium with an EKWB monoblock. I have a Bitspower 360mm and 120mm rad. This is what came from my previous loop. Newly added are 6 Noctua IPCW-2000 fans, Byksi gpu cooler for an RTX 3090, and Byksi distribution plate for an inWin 905. I am using PrimoChill UV Red fittings for 1/2" OD rigid tubing.
For the copper I am using 3/8" type L that I am annealing then bending. I did underestimate the amount I would need as 6ft wasn't enough.
The copper isnt new to me, but bending it and electroplating it is. So I don't really want to diary my failures if they happen.
The color scheme is nickel/gray and red. I was thinking about painting the pipes red rather than electroplating.