Hi Stephen, of the options you listed, there are a lot of research gaps in the use of diverse cover crops in building soil organic matter. It’s basically ‘conventional wisdom’ in the soil health/regen ag community at this point that a multispecies cover crop will provide more soil/ecosystem benefits than a single species. Yet most of the research I’ve seen (I’m in Iowa, midwestern U.S) on multispecies covers finds little/no benefit when it comes to increasing cover crop biomass, improving f:b ratios, increasing SOM, etc. Why is this? Are we measuring the wrong things? Are studies not long enough to detect differences? Are we not taking a systems approach? Or are we just wrong, and multispecies simply does not provide additional benefits or is actually worse in some situations? Would make for an interesting thesis. Good luck!