The best Bollinger Band setting is a 20-period simple moving average with bands placed two standard deviations above and below, the default John Bollinger himself uses. The 20-period SMA with 2 standard deviations is the widely accepted best baseline across markets.
Scalpers often tighten to 10 periods with 1.5 standard deviations, while position traders widen to 50 periods with 2.5 deviations for long-term trends.
Stray too far from defaults and you stop seeing what most traders see, which changes the buy and sell signals you react to.