I'm not familiar enough with Mac's to offer an equivalent to Glasswire.
Glasswire is supposed be coming out with a Mac version but I'm not sure of the timeline.
Another alternative of course is to measure usage by all devices right at the router.
I have an Asus (RT-AC3100) that has the Traffic Analyzer feature that tracks usage by device and also by application within a device:
Individual device statistics:
Detailed device usage: