It really depends on what your goals are. In general, you will find that the DevHelp prefix is used for C language bindings and DevHlp is used for Assembler bindings.
You can see this pattern if you look at your:
https://www.edm2.com/index.php/DevHelp_ProcBlockwhich looks to me as if it came from pdd.ref.
Notice also that the Assembler bindings are listed before the C bindings implying that they are more likely of more interest. This is part of history. The kernel and device drivers were originally written in assembler. It was only later that C became more widely used for device driver development and kernel development. It would not surprise me if an early version of pdd.ref only documented the Assembler bindings.
This evolution shows up in early books such as Ed Iacobucci's "OS/2 Programmer's Guide" which discusses writing applications in C and Pascal, but all the examples are in Assembler.
The items in red are another case of inconsistent naming. DevHlp_SortReqPacket is really DevHlp_SortRequest or DevHelp_SortRequest which is in the wiki. FWIW, DevHlp_SortReqPacket is a better name for the request, but it appears IBM never got around to updating all the references DevHelp_SortRequest, assuming that was the plan.