few questions, do you live in a house, condo, etc. are the walls drywall or something like plaster with rebar re-enforcement? How much space between the AP (wifi box) and the cameras?
Others have mentioned, get the old device to 5G band, if you can get a .n usb wifi attachment to work great.
Asus and others make systems with more than one AP, basically you build cells and the devices roam, the cells use 5g bandwidth instead of wire to communicate with the "controller" ap. I run .ac stuff and newer systems will take advantage of 3x3x3 where the radio is using more than one "link" to the ap to get more data through.
this is helpful with cameras and moving video around. The higher end consumer stuff also has features built in to deal with legacy clients.
I use txc, they suck balls, most ISP's do, from home isp to L3 and the rest who drop fiber into datacenters, pain in the balls to deal with.