LP's default is parallel in the middle switch position.
I'm all for experimenting but I think two hums in series would be mud mud mud. I've tried single coils in series in a strat and it was not a useful sound for me.
If the two coils of a humbucking pickup are wired in series (like Les Pauls, SGs, super distortions, JBs, etc.), they will have more output, a better signal-to-noise ratio, and more bass. Parallel wiring will have about 40% less power, more treble, and a less favorable signal-to-noise ratio. Both will be humbucking.