Good quality DC cable should have solid-core conductors. Also, you really don’t need 12awg. Actually, you should avoid solid-core conductors that are this thick. Even though it’s DC, it still has a very high frequency draw (for high frequency audio transients). Thicker gauge conductors will not be able to provide high frequency charges as well.
Your choices of Type 4 or CV4 would be perfect for DC cable. They use a combination of 20awg and 17awg in a star quad configuration, that gives you a total 15awg cable. You don’t need more than this for DC on a preamp/source device. The CV4 is discontinued, but it uses better copper (Perfect Surface Copper, which is Audioquest’s version of OCC). The Rocket 33 might give you more total AWG, but it’s not a star quad configuration. In my opinion, you really don’t need more than 15awg for DC.
I generally use 20awg solid-core conductors for both DC and A/C cable. It is the best compromise overall. The 17awg in the CV4 would help low end.