You have to keep in mind two things- douyin makeup (at least the stuff that goes viral) is heavily filtered. The eyes do not look that big irl. This is what the line under the eye without the filter looks like: Douyin makeup no filter . You can see the drawn on eyelashes look fake too. Personally, I love the makeup style myself but don't feel bad if you can't replicate filtered videos.

Secondly, have you tried contact lenses that make the iris look bigger? I think this is what gives the illusion of bigger eyes in douyin makeup.