My experience with WatchGuard Firebox has been that it operates similar to other firewall services available in the market, such as Palo Alto and Fortinet, however, it does not provide the same level of throughput and features.
We are using it as a firewall, enabling geofencing, creating policies to allow or block traffic, and setting up site-to-site VPN connections on the box. WatchGuard Firebox is deployed on-premises, as it is a hardware box.