1. I will be more clear because, i think I misinterpreted your first post about WebP. For most of my images, I'm using: WebP, lossy files, compensation 6, quality 90%, using the program Krita.
Unless you have a configuration I haven't accounted for, any quality improvement will come at the cost of larger file sizes.
2. Regarding 1080p, it's true that there are more devices than I initially thought with that quality (I had to check the statistics on that). But the other point I mentioned earlier still stands. If I raise the quality to 1080p, that translates to larger images and videos, which leaves me with less space to work with in itch.io.
I'm not against the idea of changing the project's quality. But considering what's required, at best this will be something I'll implement in the future, and at worst, it will be something to keep in mind for future projects.