New G100 owner and I too was experiencing problems. Also I do have. Deco Mesh Router axe5400 (XE75 Pro). I posted my solution on this forum ( search G100 HomeKit Performance Issue). I decided NOT to use IoT nor Guest SSID so that I can change the Deco Node that the camera is connected to.
Anyhow, my solution (tested a few times!) involved how to setup the cameras. I found that you need to connect the camera to the Aqara app first then with the Aqara app select the camera and specify to connect to HomeKit. Doing it this way you NEVER use the HomeKit QR Code on the camera. Don’t know why but using HomeKit app and adding accessory (then uses the HomeKit QR code) caused alot of grief.
Hope this help your situation.