In my testing, compression using level 14 is almost 3x faster than level 19, while compression ratio is only about 2% lower. In my opinion, it's definitely worth it.
This revert commit 9d73f302f8
squashfuse_ll causes some weird filesystem access issues. For example, some applications are unable to access /usr/share/alsa when the squashfs image mounted with squashfuse_ll.