A chubby face is one that is rounded out by fat. It could be a child with baby fat or an adult with large cheeks. "Chubby" does not imply that the person is unhealthy, although an overweight condition can lead to problems over time.
If I heard or read "bloated face" I would assume that the person's face had swollen through some sort of disease, illness or reaction to something such as medication or a bee sting. A dead body might have a bloated face as well after exposure to water or after decay had set in and gases had formed.
I apologize for being so graphic but "bloated" is an unpleasant word that brings to mind unpleasant images. I can imagine it being used for someone who was severely obese and also looked unhealthy but I would never use it in place of "chubby".