Running CSpect on Windows is pretty much download and go, but on MacOS you need to download some additional support, specifically mono in order to run the Windows .exe on MacOS. This page here, describes downloading mono using homebrew, but when starting it up it would give a segv error and crash. Instead of installing Mono via brew, download and install using the latest .pkg installer from here. It’s possible downloading via brew misses some needed dependencies, but the .pkg installer has everything needed.
To run with the Next rom I downloaded, I used these options:
mono cspect.exe -w3 -basickeys -zxnext -nextrom -mmc=sn-emulator-22.10a.img