mm, its kinda difficult question to be answered. But, through examples will see if it turns more clear for u: Matrícula, we used this word when we refer to the registration code from a car, "la matrícula del vehiculo", also, when we start university, fees that are paid at the very beginning we can call it "la matrícula de la universidad". There's another example, lawyers, doctors, and engineers do have "matrícula" which is the registration number they have. However, if we say "la matriculacion de la universidad" it would be the same, both are nouns, females, so no differences between these two words thus.
Enrolment rate would be "la tasa de inscripcion" this word, tasa, we also use it for birth rate "la tasa de natalidad" and some other cases as well.