Rogue Amoeba produce quality audio software for macOS.
I personally use Loopback to route audio around inside my Mac. It works great for live streaming and setting up a mix minus for show guests.
I’ve considered getting Audio Hijack too as it allows you to use audio plugins in real time.
They appear to be macOS 10.13 (High Sierra) ready with all of their software which is a fantastic effort. Here’s a clipping from their email newsletter about compatibility:
Apple is shipping MacOS 10.13 (High Sierra) today, and we’re fully updated for compatibility. Each of our apps has initial support for the new operating system, so we’re ready to make the leap to High Sierra with you.
Nicecast is a great bit of kit for macOS internet radio streamers.
Take a look at their sale page as you could get up to 60% off which is a great deal 
I don’t have any affiliate link with Rogue Amoeba but love their products so wanted to share the good news with you. Let me know if you use any of their software yourself?