Which resistor value is used for which motor in Power Functions 2.0?
M Motor (Powered Up/WeDo 2.0)

The M motor has a 2.2kΩ resistor between pins 5 and 6. Pin 6 is connected directly to pin 3.



LED Lights

I don't own any lights yet, but according to this post, they also use a 2.2kΩ resistor, but in this case it is between pins 5 and 3. This pulls ID 1 to ground. Here's the full circuit diagram:



Train motor

The measured resistance between pins 5 and 6 shows an open circuit. Pin 5 is connected directly to VCC, and pin 6 is connected directly to ground.



Other components

I wasn't able to determine any sort of passive identification on any other components (Boost motor and sensors, etc). My guess is that these have an onboard microcontroller and use an active handshake before establishing a data connection.

Summary

M Motor
3 (GND) ─────┐
4 (VCC)      │
5 (ID1) ─2.2k┤
6 (ID2) ─────┘

LED Lights
3 (GND) ─────┐
4 (VCC)      │
5 (ID1) ─2.2k┘ 
6 (ID2)

Train Motor
3 (GND) ───┐
4 (VCC) ─┐ │
5 (ID1) ─┘ │
6 (ID2) ───┘