I had Spyres that came spec'd with my Tiagra 4700 equipped bike from Giant. They worked but I never liked them, tried upgrading to TRP HY/RD. Better but still far, far worse than full hydraulic. And yes, Giant used Jagwire compressionless brake housing, as did I with fresh housing when I installed the HY/RD caliper. I've seen it said that the Spyres and HY/RD are the best mechanical disc brake options, which didn't inspire any confidence.
Maybe I needed to experiment with more pads and rotor combinations, but I bought two full hydro bikes after that Giant and sold it to thin the herd, so my mechanical disc brake experience is over for good.