I don't think you will get per device stats, but setting up the required products isn't too hard.
To enable telegraf logs in Pfsense just enable it
System, advanced, notifications, Enable Telegram Notifications - there are also instructions on how to configure the APi key.
It sounds like you have at least part of this.
You need to make a dashboard in grafana of the data you want form the influxDB - there are already pfsense dashboards you can import, but none I've seen do per user stats, that's where ntopng comes in.
Curious, what are you looking for in the per device stats, for a few devices it's fairly straightforward to quickly glance at them to see traffic, but when the network is larger, looking at all devices traffic will be a nightmare, so perhaps an understanding of what you are after will help.