Question 1 - which functions do these two parts have?

Short Answer:
Together they make sure the CPU is getting the exact amount of electricity it needs in order to prevent errors.  Higher-quality components in this area are preferred by overclockers, because as the CPU is pushed faster by overclocking, it becomes increasingly more picky about the quality of electricity it is being fed.

Longer, more detailed answer:

The larger parts (FP4-10CH10F) are inductors.  They help stabilize the voltage going to the CPU by storing a small amount of electricity.  That electricity can be used to boost the voltage back to normal levels if the source voltage drops slighty for a very short period of time.

The smaller parts (VT1185SF) are Voltage Regulator Modules (VRMs).  They also help stabilize the voltage going to the CPU.  They are small chips that contain components.  They look at the voltage going in and out of the circuit to make sure the voltage stays stable, and apply resistance if necessary to reduce the voltage down to the specified value.  They check for and make corrections a certain number of times each second, and in systems like the SR-2 the frequency of these checks and balances can be changed in the motherboard BIOS under the heading "PWM Frequency".  (usually hundreds of thousands of times per second).  Higher frequencies produce more stable voltages to the CPU, but cause the Voltage Regulator Modules (VRMs) to produce more heat.

Question 2 - which part is known to get very hot?

The Voltage Regulator Modules (VRMs) are the parts the produce the most heat of the the two.

The inductors usually don't get warm enough to warrant a heatsink, however the voltage Regulator Modules can get quite hot, and are usually covered by a heatsink.

http://www.hardwaresecret...geview.php?image=26259

In the picture linked above, also from the article you linked above, you can see the Voltage Regulator Modules for each CPU being covered by the taller heatsinks next to each CPU socket, while only six of the eight inductors are covered by the same heatsink.
Generally speaking, the higher you set the PWM frequency in the BIOS, the warmer the voltage regulators get.