1. to go with the trend is always the safe move, regardless of TF (the rest is riskier)
2. OB/OS is a concept that was never true or logical and should have been given up a long time ago.
Actually Stoch above 80 means: extremely high momentum and under 20 means: extremely low momentum.
This is why some buy above 80 and sell below 20 (but to me this is no sensible approach either, as the move normally is much longer etc.)
You want to sell into falling momentum and buy into rising momentum (and stay in the trade until the rising/falling fades) - that is the reason why indicators showing a change of colour on slope change are most logical.
Instead of arbitrary thresholds (for example OB/OS) you need a depiction of tradable areas (rising/falling slope).