m43 question: I use the EM5m2 with the Oly 60mm 1:1 macro lens. First point is at 1:2 ratio, it has the same magnification as a Nikon FF 1:1 macro if the cameras have the same megapixel rating. In the 1:2 - 1:1 range on the oly, you are getting more magnification because the sensor is smaller. For a DX, it's not quite as much extra bang in terms of magnification. You get a lot more DoF because you're using a 60mm instead of a 100mm or 105mm. The downside is the lens is manual focus in the 1:1 - 1:2 range. I still like my d850 w/ Nikon 105mm VR macro better, but it weighs a ton more, but I like the results better.
You can also get some pretty good shots with the Panny 100-400.
Nikon: The 105mm VR lens is awesome. I shoot it around 1/60th at f/32 - f/40 at 1:1 handheld with off-camera flash and it is amazing. What I do is use a flash cord and hold the flash with my left hand and the camera in my right hand. I use a small bounce or softbox on the flash to avoid nasty reflections. I set the camera to manual with fixed ISO (about 400 usually) and then let the iTTL adjust the flash brightness.
If I'm living large, I'll do an on-camera flash at -2 EV and off-camera at +0 EV so I get nice fill flash. This works OK w/ the 50mm + extension tube because the lens is very short. With a longer lens, it often occludes the on-camera flash so I'm using using it as a master or use the flash cord.
I sometimes use one of the
old-timey camera brackets with a flash arm. I open the arm out to the left of the camera (not above the camera like normal) and that gives me off-camera flash but in a single rig. I'm not a big fan of the lens-mounted flash rings as I find those cause too much reflection off shiny bugs.
For a DX camera, you could use a 90mm or the 105mm. The longer the lens the further away you can stand, but your DoF suffers more.
I am not a tripod macro shooter. I prefer the hand held method for quick mobility. Sometimes I might use a monopod as that is fast to move around.
Pro Tip: You can also use a good 50mm lens with extension tubes. I use the Nikon 50mm f/1.8D plus the Kenko 36mm extension tube, usually shot up around f/22. That gives a 1:1.15 (0.87x mag). It's super light and usually autofocuses pretty well. Again, I shoot with off-camera flash. You could do the same thing with the 35mm f/1.8 DX lens with either the 36mm or a 20mm extension tube, but your working distance will be a fair bit shorter.
Most things in my
insect gallery were shot with the 105mm VR or 50mm f/1.8d + extension tube, or the Nikon 28-105D lens w/ macro mode.