Is there any corelation between housing and lamp data?
Here's a quick breakdown of the most common residential lamps here in the US.


"A" lamps are mostly used in table lamps or maybe outside wall fixtures.  If the lamp is a 60A19 then it is 60 watts, "A" shaped and is 19/8 wide, or 2-1/8 inch.  Divide the number after the style by 8 and you will get the width.
"R" or "BR"  lamps are reflector lamps, thin glass.  If the lamps is a 75R30FL then it is a 75 watt "R" style, 30/8 wide or 3-3/4 inches.
"Par" lamps or Parabolic aluminized reflectors is a hard glass reflector lamp, where the lens of the lamp is a separate he piece from the rest of the lamp but not removable.  Because of the different type of lenses this style offers more directional control of the beam spread.  Everything measures up the same as the other lamps, the difference is that the part number will usually give you the degree of the beam spread like a 50PAR20/HAL/NFL30 except the HAL is halogen or capsylite, the NFL is narrow flood and the 30 is the 30 degree beam spread.


I cannot answer the question about the thermocouple that protects the fixture from over heating.  I don't know what my attic temperature is, mostly because in the summer time the ambient outside temperature floats between 110 and 120 most of the day and about 2 months of night time temperatures in the high 90's at midnight.  It's the same can as what you buy.