502 Bad Gateway Nginx Reverse Proxy
I think your networks command is wrong in the first compose file
networks: webproxy: external: trueThat specifies a network named webproxy that must exist. (Presumably you created it?). However, you don't attach any containers to that network.
The other compose file has
networks: default: external: name: webproxyWhich does the same thing, except that all the containers are attached to the default network automatically. So making the first file match this may clear up your issue (though I haven't looked into what that magic nginx config generator does ;) )