The 4-794677-2: The 3.00 mm pitch (0.118") and 12 positions in two rows set the PCB footprint and the board-edge clearance needed for the right-angle orientation.
Shrouding and board lock — what they buy you on the board
The 4-wall shrouding guides the mating receptacle into alignment and protects the male pins from bending during blind mating or harness assembly. The locking ramp on the header mates with the receptacle latch, giving an audible click that confirms full engagement; useful in applications subject to vibration.
Current rating — why it says 'varies by wire gauge'
The header itself does not set a fixed ampacity — the current limit depends on the crimp terminal and wire gauge used in the mating receptacle. For a given wire size, the temperature rise through the contact interface and the housing material (UL94 V-0 nylon) determines the safe continuous current.
Temperature range and plating
The tin-on-tin contact finish (100 µinch on both mating and post sides) is cost-effective for moderate mating cycles — expect a few hundred cycles before wear-through, adequate for field-service connectors that are mated and unmated occasionally.