For my rear Spyre, I just got a set of
Jagwire DCA016 : Mountain Sport brake pads, as they were recommended by the LBS. Whoa, Nellie, these seem to add real power. They are steel backed, and aren't particularly light, but they provide a
lot of confidence. Whisper quiet too. I'm sure I've seen more impressive $20 upgrades, but I can't recall any.
With these pads, it seems that serious engagement requires less lever travel. If your Spyre is mushy or weak, I'd recommend giving these a shot.