I know you check version and “v” and set-up WiFi “w” via serial. Is there a way to trigger dfu mode via the serial in the initial listen mode out of the box?
I haven’t tried if from listenong mode, but normally setting the COM baudrate to 14400 puts the device into DFU mode
Yup. I just checked it and connecting at 14400 baud will invoke DFU mode even when in listening mode.
I am working on windows there a serial program you recommend.
You can use PuTTY, but I just use this mode COMx 14400 (where COMx is your devices COM port) in the command line
Why does Particle still use 14400 as the baud rate? 19200 is a much better baud rate because it is more compatible for Linux and more memorable.
You need to ask Particle that.
On the other hand, why does Linux not support 14400? 
Why would 19200 be more memorable?
120² = 14400
28800 / 2 = 14400 (28800 = YModem Mode )
Granted 19200 is more common, but exactly that may be part of the decission - use a less common one (but still standard) to keep interference with other stuff at a minimum