I had many of the same problems with speed and signal strength after installing the system. The techs while where very professional, installed the Netgear router between the Comcast Cable Router and my Apple Wireless Extreme. For months my speed was slow. Bought a new $175 AC dual band router but still slow. I removed the Netgear Security Router. Bang, speed back up to 50+ Mbps throughout the house. I called XFINITY Home tech support. They agreed that with the Arris Comcast Router the the wireless gateway needed to be connected directly to the Comcast Cable router. Then connect the security router to the wireless router to one of the free ethernet ports.
No problems so far. I do not have cameras.