So you're installing OpenWrt to get control of your gaming/voip/video conference performance. You want to understand how well your connection is working...
https://packetlosstest.com seems to be a useful if basic test site that sets up a WebRTC connection between your browser and the server, and then just sends UDP packets back and forth, and measures timing and packet loss. You can turn any speed test site into a speed test + latency/reliability test by running the speed test while you run the webrtc packet loss/latency test.