If you book non refundable and the price goes down, can you cancel and rebook with ecredit?

Doing BOS-FCO next month and currently if I did comfort plus going to FCO and premium select going back to BOS, it’s currently $1700 or $2000 for refundable (comfort plus both ways is actually more expensive so that’s why I’m doing premium select going back). If the price were to go down, if I did non refundable, am I able to cancel my booking and rebook with the ecredit?

Also just trying to see if it’s worth just doing refundable for that price. I don’t foresee me having to cancel my flight/trip but I know anything could happen.