There're 12 Volt 5-6.5 A SMPS availabe but need is the lower 6-9 V, can we just lower the R parallel to the last C on output or not (due to riskier to safety)?

 

There're 12 Volt 5-6.5 A SMPS availabe but need is the lower 6-9 V, can we just lower the R parallel to the last C of output or not (due to riskier to safety)?

Why would you think that? An SMPS is carefully designed an optimized for a specific result. You cannot go changing components willy-nilly expecting to successfully modify the behavior without some understanding of what to expect. The output power level is high enough to be dangerous if you make a mistake.

In some rare cases you might find an SMPS that has an adjustable output. In no cases would you be required to replace one component with another.

 

lower the R parallel to the last C of output

Any resistor in parallel with the last capacitor would be a load resistor.
No - you can't lower the voltage by increasing the load. Switched-mode power supplies are regulated to keep that voltage constant, and the voltage would not reduce until it was overloaded and started to current limit.

You may be able to find the feedback resistors and change them to lower the output, but that would also lower the auxiliary voltage that runs the control circuitry, and if that were too low it might stop functioning altogether.