Thanks for looking and the kind comment. Appreciated.
I find that getting the best depth of field is a bit of a balancing act. I have a few Nikon cameras, but for macro my go-to one is the D7100 as it has the highest resolution in the DX range. (I have a D500, but in this case it is not as good as I need to squeeze every bit of resolution possible). I would love a DX camera with 36MP sensor. That would be great!
The lens setup for these shots was just a 90mm Tamron 1:1 macro lens (not the newest version) with a 36mm extension tube between it and camera. A Nissin ring flash for lighting. I have an old Nikon ai-s 105mm lens which I also use as it gives very good results as well and can be picked up at reasonable prices.
As you are aware, the more magnification, the less the DOF. So I try to balance between going with a longer focal distance (giving less magnification) and relying on the pixel density of the sensor to maintain the required detail that I want to extract from the final image whilst still being able to crop in quite tightly.
Added to this, I usually shoot at around an aperture of f22 which also extends the DOF. This does require a more powerful burst on the flash though (not so good if you are trying to use the flash to freeze action).
The following example is shot with the Nikon 105mm (and 36mm extension tube) at f16 on the D810, but at a much closer focal distance (hence greater magnification). You can see that the focal plane is much thinner and that the back of the fly (only millimetres behind) is already loosing focus.
Thanks again and hope that helps.