Yes they're there! They're just not in /etc on a Mac - this is because you can't write there anymore in the latest macOS. Apple has locked that down a lot even before Catalina (system integrity protection)

I think they're under /usr/local/opt or something.. This is a homebrew thing, nothing to do with tinc really. I'm not on my Mac now so I can't check, but they're definitely somewhere.

I tried to find out which udp/tcp ports need to be open for tinc to work, but could not find anything in the documentation?