I already fixed this issue, but sharing my experience in case someone else has similar issue.

ISSUE: All Tapo cameras (C260) were unusably slow when viewing live or stored footage when connected to same wifi network as the cameras. It would take 20-30 seconds to load the first frame of the live view then update one frame every ~20 seconds. Disconnecting phone from wifi to use cellular would fix the issue. Pinging the camera on LAN has a latency of 500-1000ms despite the camera being less than 1 ft from the router. I noticed the camera always used 5ghz connection, not sure if this matters.

SOLUTION: I just changed my xfinity provided modem/router to bridge only mode (disables wifi) and used another router (tp-link AX1800) and that fixed the issue. The camera auto uses 2.4ghz and has a ping of like 5ms on LAN.

Xfinity provided routers don't allow you to do stuff like changing the channel or making a separate network, so many other router tweaking solutions aren't viable 

P.S: These cameras were previously on an Eero pro 6E mesh system without any issues (I moved apartments and left behind these routers)