Which settings will give maximum range and throughput with TP-LINK W8968

I have a TP-LINK W8968 modem router. Neglecting other factors which

1. Frequency band gives maximum range 20 MHz or 40 MHz? Which gives best throughput?

2. Channel gives maximum range 1, 6 or 11? Which gives best throughput?

I have done some reading which makes me believe that while 20 MHz band is better for range 40 is better for throughput.

I am not sure about channels.

My own empirical testing did not show much difference in a low signal corner of my bedroom.