Daniel you are doing great. Good work!!
I can't speak for any files other than what I use.
Nearly 20 years ago I purchased the StewMac (SM) diamond crowning file, the straight one that these days they rounded the nose which was a good improvement. I have 150 grit diamond files for the heavy material removal and 300 grit for most things. We have the Z files and Dave likes them and I don't like them or use them now.
Keep in mind more coarse files may save time in hogging off material but they add more time at the other end sanding the scratches, deeper scratches out. So for a normal fret dress without heavy material removal I stick with the 300 grit files so I have less sanding to do.
Dave my business partner uses a power tool he invented that I will spare you the name here this time...
I still plod along by hand. No jokes please (unless they are good one...
)
Anyway my diamond files from SM are STILL sharp and I use them weekly. They have each done hundreds of fret dresses and refrets. Amortize that cost of ownership with the value received and they were one of the best values of any tools I've ever owned. I also know that SM will replace them at the drop of a hat when and if they ever need it. SM recently replaced under warranty about 15 nut slot files that we wore out but not before cutting thousands of nut slots.
So my point is that the cheap stuff may not be cheap.
Precision wise the SM stuff is also excellent and other than we "safed" our crowning files on a belt sander with the exhaust ducting removed and dust collection off.... they do an excellent job.
I use my three corner file when the shape I am getting is a bit like a school bus roof. I only use them maybe 3 - 5 swipes on a side of a fret.
For others since I know you know this Daniel diamond files are superior in really all respects to conventional files. They work in both directions and they do not chatter where the conventional files chatter and work in only one direction.
I've never cleaned my files either with the diamond stuff.
I can't comment on which of the cheaper files would work for you but in my world I only ever use medium and fat with medium being used the vast majority of time. I do use medium on Mandos too and it does a goof job.
A wider file will make a narrower crown with practice and rocking the file back and forth. A file too narrow will not work on a wider fret at all.
So to recap and be more clear all my files are SM and I use the diamond ones for crowning, conventional for a 3 corner and fret end file and none of my stuff has worn out after nearly 20 years with 17 years of that being commercial, near daily use.
One last comment. I have some files for other things that are my favorite. It's not the files so much that are special it's simply that they work pretty well and I got used to them. There is a GREAT deal to be said with getting comfortable with a tool, pool cue, target pistol, sailboat, Telecaster you name it. With my point being that how the tool suits you is part of the equation as to how well it will work for you.
If I was new to a tool there would be learning curve again for me. So not only invest in quality, guaranteed tools invest in yourselves too and what is comfortable for you, what lets you see the work piece when and where you need to see it and becomes something that you value far beyond what you paid for it.
Pick up a beater guitar to test files on the frets, put sand paper on the part of the side that matches the radius of a Fender nut and a host of other test bed and learning activities. When I started in the trade it was clear that Dave never threw stuff away. Now I know why we often benefit from dry runs and trying things out.