I now use PSA diamond film exclusively above 1000 grit, but I’ve never used the 3 micron stones.
If I were trying to pick a batch of stones and films strictly from the advertised grits, and if I had the micro-fine ceramics and the 1200/1600 ceramics I’d pick the following:
1200 ceramic
1600 ceramic
5 or 6 micron PSA diamond film (4,000 or 3,000 grit) on the glass side of the 3 micron diamond platen
3 micron (8,000 grit) diamond platen
1.4 micron ceramic (13,500 grit)
0.4 micron ceramic (about 60,000 grit)
If your micro-fines don’t perform as advertised, buy 1 set of Aluminum or Glass platens and set them up with 1.5 and 0.5 micron diamond PSA film.
I use 15 and 9 micron film as direct replacements for the 1200 and 1600 ceramics. Equivalent grits are 1200 and 1800 respectively. Under my microscope, they look identical. The film is just a little more consistent.
Of course your results may be different and I haven’t noticed anyone on this forum comment about the 3 micron diamond platens and how they perform during the break-in period and after. That’s one additional nice thing about film. No break-in period.