Does macOS provide a way to capture the output from a sound card? I do software FX on my guitar using my Mac and a USB interface, but the produced output sound goes back to the interface - I can listen to it but I can't record it on my Mac, only the input sound device pre-FX.

I'm aware of "virtual cables" and "virtual sound cards" but I understand Windows for instance can allow direct capture of a sound-card output. 

Is this something available on macOS and if so, which versions - and any general information I should know?
Apple's really crappy UI with useless documentation for MacOS's audio is the Audio Midi Setup.  Once you find and open it, select menu Window/Show Audio Devices. 

That in conjunction with some virtual audio routing software like Soundflower may get you want you need.