DIY AC cable...which bulk cable?

Neotech and Furutech both make a number of bulk power cables so gets complicated as some are shielded, some are not. Also different purity of copper and size of conductors, etc, etc.
I've found that the larger the conductors the more difficult to build the cable so go only as large as you need. Maybe shielded for source components and larger, unshielded for amps.
I like the Neotech cables because they come wrapped in Techflex which is another cost with other brands mentioned.
I've built 2 Neotech NEP-3001 and 2 NEP-3002 (all shielded).
Thinking about building a Furutech FP-Alpha 3 (unshielded) for my amp soon.

I have 2 R1s in my power supply but just my digital source components are plugged into it. My power supply has shielded NEP-3001 going into it.

As far as shielded/unshielded depends on your environment and what you're plugging into the power supply. Possible it may not matter.

Also, shield on shielded power cables has to connect to one of the connectors so you will have to unbraid it and twist into a wire to connect to ground (if I remember correctly the male connector, floating on female end). Some cables have a shield drain wire which makes it easier but should not be connected at both ends.

Caveat: Hope this helps BUT I am no expert, please consult other sources before building your PC.

Furutech also offers a number of bulk AC cables worth considering.