Channel Width sets the width for each frequency band of the Wi-Fi radios.
20 MHz is the base channel width, but multiple channels may be bonded together to increase data rates and throughput.
Recommendation
2.4 GHz: Always set to 20 MHz.
There is not enough space in the 2.4 GHz spectrum to reliably use 40 MHz channels, especially with multiple APs.
5 GHz: Set to 20, 40, 80, or 160 MHz.
A higher setting value will provide a higher throughput.
Some clients may not fully support 160 MHz channels in 5 GHz, which requires DFS (Dynamic frequency selection).
A lower setting value will support higher client density.
6 GHz: Set to 80 or 160 MHz.
There is a lot of available spectrum for wide channels, and no requirement for DFS (Dynamic frequency selection) or AFC (Automated Frequency Coordination).