Was thinking of doing the same thing with one of my old guitars. I was planning to remove the frets first before sanding the edges but I also wanted to flatten the fretboard radius a bit. I would think it would be tougher to achieve a uniform rounded edge with the frets still in place.
You might get more response if you post this question in the build and repair forum.
https://www.acousticguitarforum.com/...splay.php?f=44