The mail threads and chat screenshots show his side.

The equivalent of i3 on Wayland is Sway; it’s even compatible with i3 config files, it’s a true successor. Hyprland is popular because of the eye candy and its rapid adoption of features which patch over some of the gaps in Wayland functionality. However I think those advantages have become fewer and farther, I personally use sway and if I wanted the visuals I’d use the swayfx fork

Yes. Also plus eye candy with hyprland. Sway is the i3 experience on Wayland. The official roadmap for i3 is to fall into obscurity as Xorg goes away. They explicitly call out that other things exist for Wayland and adjusting i3 would distract resources from those projects

Mostly, yes, X vs Wayland. Hyprland also has a lot more eye candy in the way of window animations for snapping, dragging, etc. I find the Hyprland config file simpler too, but that's just me.