I ordered S sized (EU) jersey, which is my normal clothing size and it turned out to be the right decision.
The fit is form-fitting and the jersey really shapes according to my body. Also, I really like how snug the sleeves are and also the fit across my chest and waist. It does not restrict my movement and is not baggy at the same time.
I have seen a few comments about other cyclists struggling with getting the size right. If you are not sure which size to get then consider ordering 2 sizes and then sending one back.
I personally could not be happier with the fit so scoring it a 10/10.