I can confirm the manual potentiometer brightness adjustment capability as is described in the Winstar OLED App Note Ver. 3.4 (2015/01/27). Page 8 illustrates wiring, but it notes that an option jumper on the PCB needs to be moved from position "JV" to position "JV0". I can confirm that this jumper relocation is necessary in order for the manual brightness adjustment to work. I cannot yet confirm command based brightness control with the WS0010. Would you please specify the manufacturer and model number of the 2x16 display you are using, and are the commands that set brightness as you specified in hex? That is, for example, is your line of code "LCDOUT $FE, $32" to set maximum brightness?

I am using a Vishay 2x8 OLED display (which uses the WS0010 controller) in the serial SPI connection mode, and will post a code example for this in the Forum's Code Example section.