I don’t have native experience of this fish but from all the reading I have done, all four species are reported to have maxillary barbles anything between none existent up to reaching the eye.
P. Micronemus should have a defined black spot before the caudal penduncle.
In my humble opinion this could be p. Paravanalis, the smaller growing member of the group, but I honestly still think it looks like p. Apogon to me.
Each species have different length of maxillary barbel except for parvanalis & micronemus, they're the same length. But then you need to look at other aspects such as their type locality. Parvanalis only found in Borneo, while other 3 the rest of SEA.
The farms that I know that breed this Sheatfish are in Thailand, they're supposedly food fish, great tasting fish. They will use cheaper sources & easy to come by. Most of Phalacronotus in the hobby are from farms, that's why you can get cheaper prices, very rare you see wild ones. More so to think it's not parvanalis.
As for the micronemus, it said that it had dark spots at CAUDAL FIN BASE, not caudal peduncle. So the dark blotches on the caudal fin base are shown its the true species. With that long barbel, it's a P. micronemus.
