Need to measure data consumption by devices connected to my router

[glp3]

I have a RBR20 with RBS40 and RBW30 and have around 25 devices connected to it. I am consuming more than 2 TB of data a month:-( and trying to isolate which devices are the culprit. I turned on the Traffic Meter on my Orbi app. But that doesn't gibve the data consumption by device over time. I have 6 TVs at home out of which 3 have Roku Streaming Stick+, 2 have Roku Ultra and 1 has a built-in Roku app. No cable /satellite TV but have YouTube TV in addition to Netflix, Hulu, Prime, Hotstar, Willow, Bloomberg, etc. But at any given time only 2 TVs are streaming most of the time. I realized that we have to go to the Home screen on Roku before turning off the TV to prevent it from consuming data even after the TV is switched off. That should save a lot of data! But is there any way we can collect data per device?

[CrimpOn]

Alas, the Orbi product does not collect usage by device. This is one of the most frequently requested items on the community forum "Idea Exchange".  https://community.netgear.com/t5/Idea-Exchange-For-Home/idb-p/idea-exchange-for-home 

There is a feature in the free Wireshark program that will identify the "Top Talkers" on a packet capture.

The idea would be to capture about an hour of data using the Packet Capture feature on the Orbi debug page (http://orbilogin.net/debut.htm), save the debug file, then open the LAN.pcap file with Wireshark.  This is tedious and (obviously) is only a small sample.

If the issue is that the ISP is charging for overuse, there are routers which do collect data usage by device.  This article mentions two possibilities, one under $60 and one under $120 https://www.wirelesshack.org/routers-that-can-monitor-data-bandwidth-usage.html 

The concept is to connect this router to the ISP device so that all traffic flows through it (disable the WiFi feature of course).

Then place the Orbi into Access Point (AP) mode so that the new router assigns all IP addresses.  It will then record the data usage by every device on the network.  If my internet were costing me $100/month extra because of overusage, I would go this route and probably break even in one month.

Aside from this one article, I have not done much research into which routers might be the most cost-effective for such a project.  There was a forum post a couple of years ago on this topic tha mentioned which router was used, but I have not found it.