T.I.G. Stack for OPNsense Firewall
Telegraf Agent + InfluxDB + Grafana stack to build dashboard from for my OPNsense Firewall & Router

Telegraf Agent --> InfluxDB
With my influxDB + Grafana connection already set up, I just need to create an OPNsense bucket in my InfluxDB container and connect it to a Telegraf agent to my OPNsense set-up. 
First, download the Telegraf plug in to your OPNsense machine. Navigate to System ---> Firmware ---> Plug-Ins and download Telegraf:
Once installed, navigate to Services ---> Telegraf ---> General and enable the agent:
Save settings, then navigate to Telegraf ---> Output. Enable and enter connection information for your InfluxDB2 container:
Save settings, then navigate to your influxDB2 GUI and select your bucket to confirm you're receiving data:
All set, you can now start building your dashboard with Grafana!

The Dashboard
In Grafana, either load a template or build your own custom dashboard by navigating to Home ---> Dashboards ---> New:
Given that OPNsense was forked from PFsense, you can either find PFsense dashboards and configure variables accordingly, use OPNsense templates, or just build your own dashboard. I used OPNsense Metrics. Load the dashboard and configure however you'd like!