Inductive Proximity Sensor Technical Details Request (curiosity)

I'm not asking because I have any issues, I'm just looking to understand, and optimize the installation.

I bought some inductive proximity sensors. I wired 3 PNP N/C in series with a 47ohm pullup resistor(A61 included that resistor). They seem to work fine off of the 5V on the BOB (C35).
A couple questions:

1. The 47 ohm pullup resistor seems low, compared to all the other configurations I've read about in other threads? (10K, 22K, 47K, ...).
   
   • Why so small, and are there any assumptions to be made about the accuracy/reliability of the circuit?
   
   
2. What is the best "shape" for the... pin?... effector?, (what do you call it?) that the sensor "sees". (most accurate in our case)
   
   • Does this inductive proximity sensor detect better: edges, points, areas? I see alot of people use round head bolts, nuts, pins, the mill itself, ...

Thanks,

47ohm resistor directly across 5v would be ~100ma, but there is the impedance of each transistor and any other internal impedance of the BOB that also comes into play.
The max load of most O.C. Prox is greater than 100ma.
Manufacturers usually state the sensing distance and it is based on their published target details, for e.g. Balluff state a square piece of M.S. 1mm thick The length of the sides corresponds to the dia of the active surface.
Al.