Ah, found the toggle down at the bottom of the complication config screen. I agree with with @Cricet1979 that separate controls for the large and small complication would be nice, if feasible.The small complication should be toggle-able to either feels like or actual temp, just like the large complication. Unless you're asking for separate toggles, so you can have the large complication showing feels like and the small complication showing actual?
I wish all apps had threads like these. Sometimes you send in emails to the developer and hope they even see it. Here: complete interaction!