I've taken a few measures to help with the Nest cameras but you are correct, they are by far the least favorable part of our setup. As for AT&T, and I can't believe I'm saying this, they've corrected many of their router issues over the past 2 years. Early on we tried them but failed miserably and moved to Spectrum for a while. Spectrum only allows for 35Mb uploads so we had to find an alternative. We moved back to AT&T about the time they fixed multiple firmware issues and have been happy ever since.
I had a couple 10G devices prior to adding the new AX89X, now I get to go wild and expand it even further. On one hand, the network can be a PITA but on the other, it's a fun, albeit expensive hobby!