The DS18B20 is a digital sensor, several of them can sit on the same bus.
It will require a bit of ground work to map a sensor ID to a location (heat it up and see which changes).
I would recommend never using parasitic power, and just connect power+gnd+signal to each sensor.
A star network is advised against in the appnotes, but can work depending on your total wire length and sensors.
For max range, I would run the DS18B20's on 5V, but if you prefer they can run on 3.3V also.
The photon has some 5v tolerant pins, so a pullup to 5V should not hurt it and will give larger signal-to-noise ratio.
If you need more than 30meters/5sensors I would recommend to have several busses, either by using multiple pins, or using hardware to isolate the busses from each other, for example an analog multiplexer.