Hi greyperson.
I look forward to hearing how your layering experience goes, and helping you to troubleshoot in any way that I can.
I did a little research and found that Ken mentioned here to a 5’10" 260 lb sleeper that L&P Quantum Edge® Elite Combi-Zone pocket coils are more than sufficient for your weight range. He also had some interesting thoughts about the ideal ILD for Dunlop layers that you may find relevant to your own experience.
As for foam under the coils, this is meant to offer stabilization to the coil system and is generally preferential. Some people like it, some people don’t, and usually in a proper encasement it’s not entirely necessary.
NikkiTMU