>(1) Use only 5GHz for Wi-Fi. Turn off 2.4GHz WiFi - it's an overloaded, noisy spectrum band.

This is an extremely bad idea in some countries, or if you’re not careful which channel you select. In nearly all countries some of the 5ghz channels are shared with RADAR and require DFS. In some countries (eg Germany) all of the channels do.

The idea behind DFS is to detect radar pulses and then shut down the network for a period of time, this can be triggered by radar or interference.