Glufoss and Smooth Operator are kind of "psychoacoustic" EQs who will"listen" and try to make a mix more pleasant to the ear.
Smart EQ is a "regular" EQ that "listens" to your sound source and will create an EQ curve based on a learning profile (kick drum, snare, guitar, vocals...).
Smart EQ 3 can also do unmasking EQ between tracks (up to 6) that you can place in three levels (front, medium, back).
What I noticed is that Smart EQ 3 produces different results than Smart EQ 2 using the same profile and audio source (a simple sampled kick drum for example). I found Smart EQ 2 to produce more pleasant results. I reported this and am waiting to know if it's a bug or a feature