The main difference between them is what's played on the second triplet of each count. On the flam accent there's a single stroke and on the flam drag a double stroke. You can go from a flam accent to a flam drag by doubling the single strokes on the second triplet of each count.
What is flam in music?
What Is a Flam? A flam (or flam accent) is a drum rudiment wherein a drummer strikes a grace note just a split second before striking the primary stroke. Drummers use flams to thicken the sound of notes they play, producing a longer note than they could with a single stroke.
What is a ruff drumming?
From this we get the shortened term "ruff," which means several quick grace notes on a drum preceding the accented note - a ruff can be from one to four strokes played as quickly as a roll. ... The wiggly tremolo sign above is meant as a drum roll.