There should be no distance between both people, this is unlike the "man pat" where distance should be maximised as affection, and respect are not part of the relationship. It could even be possible, with the "man pat", that both parties to the hug are politicians or arch enemies.
A marshmallow hug should see both people lingering for a squeeze, a giggle and a cheek smooch.
Marshmallow huggers are generally warm people, and dislike those who "man pat".
*Flower and bumble bee throw their arms around each other, squeeze, face smooch and giggle with glee due to the happiness created by marshmallow hugs*