Don't cancel yet.

Do your research and figure out exactly what the rules are for each ticket. Both how the cancellation is handled (refund vs. credit, change fees, etc.) and exact timing by which the cancellation must happen (e.g., specific time of day and date based on the flight times).

Then wait, and watch the flights. If something gets delayed or canceled, you may get better overall terms and conditions than what's on your ticket. If there are normal operations, then you cancel and live with the rules of your ticket. If either airline experiences a significant schedule change, that can also be an "out" for you. A five-minute change won't get you out of a nonrefundable ticket, but a 2-3 hour change could.

In my United-flying years, a phone agent could instantly put full credit back into a PNR and/or allow a rebook with no fees if my flight was canceled or delayed by a significant amount. There was also a process to pursue a full refund but it was a separate department. Since I was 1K, flying every week, I just accepted credit for rebooking.

Don't know how Economy Plus fees are handled.