PKGNG and
ports-mgmt/portmaster and not competing solutions to ports management. The first one is nothing but the new packaging backend (in other words tools to create and install binary packages) to the ports system and the latter is for those who want better control over ports building because the basic
ports(7) infrastructure lacks some features that one would want. The reason why
pkg wants to install conflicting packages is simply that you're mixing ports and packages that have conflicting options and/or dependencies. At the moment it's not a good idea and you should stick to using only the official binary packages or build all and everything yourself from ports.