When I set a profile picture for a contact in emClient, the picture quality is very bad when it is synced with my googlemail.com account. However, if I set the profile picture of a contact on my Android 10 smartphone, the avatar picture quality is much much higher.
There is no difference in quality for my avatars where they are the same, I use
several across different accounts, no matter if eMC, Gmail or here, they are all
as clear as you see here, as they are also on both my iPhones.
The avatars are all generated by gravatar.com, if you are not using this service
it would be an idea investigating.