Yes, lots of the oldest school American ones are. Cause : and ; and = are all useful for eyes.
It depends on context. :) and :D are real emoji workhorses. Sometimes ending with :) just means like 'yay happy, see this is a good thing' when otherwise, in a text message, someone might read a negative emotion into things. Because text strips a lot of tone out of things. :] is just a variation on that, a sorta different looking smile. Personally it feels like the start of a smile, when the corners of your mouth crinkle up. But that's a sample size of 1 thing. Sometimes it's also nice to :] because :) might be getting overused and need a break. :D has a lot more energy, sorta bouncy and excited. Extra D's just mean even more energy. It's a big grin, not just a smile.