DIY speaker wire: does insulation matter?

I'm planning to make solid core copper speaker wires and have a couple of options as to the insulation to use, and would like your input: cotton, mylar, Nomex, or mica-based.

Does the insulation material matter?
How thick should the insulation be?
BTW, what kind of voltage are speaker wires subject to?

Looking into Anti-cables, they use VERY thin PVC, I believe.

FWIW, speakers are B&W 804S, amp is McIntosh MC275, wire length will be 8 feet, wire diameter 0.098 inch (gauge 10, I believe), and I'm planning to biwire the speakers.

Thank you!