To the best of my knowledge the only functional SDR software on the OSX/macOS platform aka Macs would be Gqrx at this time. There could be something else, and you could potentially run Windows-based software in a Windows virtual machine using VMware Fusion, Parallels, or VirtualBox, but for now Gqrx is the one package I know for a fact does work. You can find more info about GQRX here:
It's fairly simple to set up as long as you read the documentation carefully and pay attention to what you're doing.
Now as for autoselecting a frequency as in locking onto the strongest one directly or even a scanning-like plugin capability I don't believe that functionality is part of the program - Gqrx is rather limited and designed to be operated "by hand" meaning manually and doesn't offer much in terms of automation but that's always something that might happen as development continues.
I feel like an idiot for saying this but there was a point earlier this year when I had SDR# running in Mono under OSX (before they changed over to macOS that is, not that it's relevant to this topic at hand). I completely forgot about it and will say I'm not sure what the state of development is at this moment but it did work given some limitations. The information that I used to get it up and running can be found at the link Eric provided above at the RTL-SDR blog website.
And yes it did work well enough I suppose, I didn't get into using a bunch of plugins like the scanning one (either of them) so I can't speak for whether or not it will work in that respect.