Out of habit, I'm always choosing the smallest channel bandwidth in my WiFi setups to optimize range rather than throughput. Now I keep reading that the channel width does not affect range.
A long time ago, I've learned that effective transmit power depends on the bandwidth of your signal, as you're spreading your transmit power over a greater frequency range. For example SSB, single side band - essentially half an AM signal, is used in amateur radio to achieve greater ranges than with wider voice modes (AM/FM). The craziest of contacts are still made using "continuous wave" with Morse code, for that same reason.
If my assumption is correct, throughput over distance would be a mixed calculation, but the lowest bandwidth should provide the greatest possible range.
Is that a correct assumption, or are routers compensating for the higher power requirements? Or maybe there's something I'm missing?