Wiki has a quick explanation about PSE-36 mode, https://en.wikipedia.org/wiki/PSE-36 seems fine for a ram disk (and likely for swap support as the 4MB page size wouldn't matter) but not so good as a PAE replacement
In our case it has sense to compare PAE and PSE-36 in a OS/2 scope but not globally.
In fact - os/2 drivers and kernel expect that physical addresses are 32 bit width. (It is possible to change but huge amount of code has to be completely rewritten.)
Thus, 4Gb+ memory can be used for ramdisk or swap area only (almost).
OS/4 Team to access 4Gb+ mem chose PSE-36 for certain reasons: access will be faster and simpler.
In case PDD and kernel gets transited to 64 bit physical addresses, PAE will be more suitable for sure.
Separately, I want to stress, transit to 64 bit physical addresses will not give some tangible gain - rather a loss. PAE pte is twice bigger then PSE-36 one. Thus, page tables will consume twice more memory (and address space too). And the system will remain 32 bits and all the problems of insufficient address space will remain. So it is senseless.