I’ve never used individual Miche cogs. Individual cogs used to be pretty easy, and cheap, to get on eBay.
But I have used 7, 8, 9 & 10 speed cogs from Shimano, SRAM, and Sunrace; although primarily 8 and 9 in 8 speed setups.
I’ve never compared an individual cog, for example a 21t, side-by-side to see if the ramps and teeth configurations from different mfg’s match. I haven’t had shifting issues, but have not tried to build a 10 or 11 speed (can’t imagine a full cog offering).
I haven’t found cog thickness to be an issue, but I don’t use standard spacers with different cog thicknesses. While it may be a bit more than most people would do, I adjust spacer width to get the correct center-to-center cog spacing.
If I do build a cassette and find a particular shift not to my liking, I’ll use the barrel adjuster to see if I need to swap a couple spacers with slightly different widths. Unless there is a finicky shifter, I have a downtube with a sloppy detent, it ends being smooth and quiet and doesn’t need any more tweaking.
John