phosh 0.13.0 is out 🚀 :
https://gitlab.gnome.org/World/Phosh/phosh/-/tags/v0.13.0
Improved call handling when shell is locked, lockscreen notifications, high contrast theme support and much more. Check the release notes.
@letterus there's also certainly areas within phosh that we can make faster or that will change in layout and hence use less resources (like the overview) but then again it depends on the details of the situation. If it's "overall slow" then it looks like a distro issue.