Say I have a spring in the shape of the backbone of DNA. If I unwind the two parts which would have more potential energy when pushed all the way down, the double helical or both of the individual springs combined?
I think two equal springs would test very close to a spring with double the spring constant. See adding springs in parallel equation.
Two springs may be somewhat less material efficient than a single spring; because the cross section of a spring wire has an area moment of inertial (just like a beam) that provides the restoring force and the equation is not linear. Think of it like the strength of a cantilever wood 2x4 vs the lower cantilever strength of an equivalent mass of four wood 1x2 members.
A reason you may want to do it would be to achieve a desired spring constant with springs you already have or within what is available. However, most of the time this is done with nested springs because the ends are typically flattened and would not permit another spring without modification to the ends. Another issue would be spring travel and fill. Notice that the green and brown die springs below would not be able to even fit a duplicate.