The spinnaker pole length should be the same as the "J" dimension as Marmalade stated. Also it should NOT be adjustable in length. Whisker poles often have an adjustable length feature..... but ... the loads on a spinnaker pole are much greater, enough to cause catastrophic failure to a multi-part, adjustable device.
I'm not sure why you think the design of the spinnaker would affect the pole length or the sail's ease of handling.
I think maybe you're confusing a traditional, racing or "symmetrical" spinnaker... which requires a pole to hold the windward clew out beyond the headstay.... with an "asymmetrical" or "cruising" spinnaker which has a defined tack and clew, and does not require a pole. The Asym's tack remains attached to rigging at the bow, a pole can be used, but it is more common to use some kind of fixed or retractable sprit with an adjustable "tack" line.
Symmetrical/pole Asymmetrical with sprit