For a deeper dive you can peruse the works that cite these articles, there's lots of research into microplastic population dynamics. Unfortunately most reach similar conclusions.
Microfiber cloths are, on the other hand, a major source of microplastic pollution. They are basically just ready-to-snap-off microplastic particles. They shed a substantial % each washing cycle. Something like 80 % of all microplastic pollution sampled in ocean water is from microfibers.
It wasn't a good fit for me. The strip of windows extending past the border of my screen, sometimes showing half a window, triggered a weird anxiety, it kept drawing my attention. I used it for about two months and then ditched it for a more traditional tiling compositor (hyprland) where windows don't overlap the screen border.
Niri is, however, very pretty from a technical standpoint. Modern Rust codebase, good code structure, very easy to understand and start hacking.
The 200-500 kiloton/year is from https://pubs.acs.org/doi/10.1021/acs.est.3c05955
For a deeper dive you can peruse the works that cite these articles, there's lots of research into microplastic population dynamics. Unfortunately most reach similar conclusions.