My apologies for the time frame of this reply. I could go on and on about workloads, people getting fired etc. But I won’t!
Referring to your questions:
The only thing I have found challenging about the finer details is the amount of time it takes. Some dies would take 24hrs or more to complete. (Now those dies take 30-40 minutes!). So if you have a lot of fine details, I do not recommend the small machines.
If you insist, here’s what I used to use on the Nomads:
.1mm is about .0035 inches! So .004 would be the minimum space required. I only ran foil stamping dies, so I had depths of .005 to .010
We used to use acid etched magnesium, but most of our runs are in the hundreds, and the magnesium dies just cannot stand up to that, along with the constant heating and cooling. Cracks would quickly form along the edges.