Not GP, but I would drop the pagination in the pop-ups. Regular Scrolling, maybe even css snap-scroll, would be more convenient.
On mobile, some of the icons are too small to be legible (e.g. „mouth“).
Overall, nice work though! The resulting avatars look great!
The main thing is to make it modeless. When there's space, like on a large desktop window, put the selector alongside the preview. Then any change in selection should update the preview without additional clicks. Basically 1 click should change a feature and another click change it to something else.
If you used it for any length of time, these things should be self evident as annoyances to be streamlined. As an exercise, try every selection for every option while looking at the preview for each result.
Move the chooser off of the top of the avatar is step 1.
Also defaulting to a mask and then hiding the UI for removing it? Makes the first chooser look like it does absolutely nothing. As it stands, it looks like only the first three are actually different.
If the first thing you click on appears to do nothing, user hostility begins already. The first rule of UI is don’t piss the user off, because it’s much harder to interpret feedback from an angry user (it’s possible, but it takes a lot more skill and emotional maturity).
Thanks for your honest feedback!
Could you don't mind giving some thoughts on improving the overall UI?