Ubuntu 16.04 - Can't connect to home Wi-Fi with Killer 1535 (QCA6174)

All though there were bugs with QCA6174 back when this question was posted they have been fixed. Granted new ones may still occur. To fix these old bugs use:

sudo apt update
sudo apt upgrade

New installations will not have the old bugs listed above and will have no need to do anything to fix the old bugs.

Contrary to your link on Network Manager Power Saving I have my card setup the opposite way:

$ cat /etc/NetworkManager/conf.d/default-wifi-powersave-on.conf
[connection]
wifi.powersave = 3
# Slow sleep fix: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1670041
#wifi.powersave = 2