Even after enabling float in the i3wm config and disabling fading, shading, and blur in picom for all "pop" windows, the overlay (both floating and tiling) flickers and generally acts weird (when sharing or viewing shared screen).
When in floating mode, it resists resizing and moving by snapping back where it was before dragging the window around.
This is the case even after reloading picom, i3 and pop itself.
One useful workaround is to make the overlay window tile on my second screen. That seems to reduce the flickering by a lot (and obviously the resizing and moving issues disappear).