I tried to play with GPUI for making a scratchpad like app with zed and It was one of the most rough experiences out there. They mention it in the readme though that it has rough edges but I hope that they make in the future more easier to tinker around.

This set of components is a nice compliment to GPUI: https://github.com/kiruhq/wgpui-component

Xilem is more like Iced but with it's own patterns and underlying graphics library.