The best synonym would be "relaxed". You can say someone has a "forced" smile when they are "trying to hard" or smiling when they don't want to. An "easy" smile would be the opposite of that; a very natural smile that they make easily.

Seems to me that it means that you always seem to be happy or find humor in things, or a "happy go lucky" kind of personality. It is a compliment.

I'm not sure, but maybe it means 'relaxed, happy, not worried, comfortable'.

I'm going to find the clip! Wait a minute! Thanks!!!

It's hard to know for sure what they meant without more context. Can you provide more dialogue or a link to the video where it is said?