Without a detailed understanding of how npc spawn works in PTS, it will not be possible to convert it normally into one suitable for L2j. I'll explain point by point.
1) In PTS there is such a thing as NPC Maker, which has a bunch of separate implementations and can work in very different ways. For example, some makers do not spawn mobs by default, some spawn a certain version of spawn at the command of other makers, some change spawn depending on incoming scripts from mobs. In general, it is quite a big problem to correctly convert the dynamic spawn of the PTS into the static spawn of L2j.
2) In PTS, a very large number of mobs spawn through the minion mechanism (For example, Konorix mobs in LOA are all minions and are spawned by a separate controller). Also, a significant part of NPCs in cities also spawn through this mechanism.
3) In the PTS there is quite a lot of extra spawn associated with events, outdated mechanics, as well as spawn associated with some instances. This still needs to be taken into account for correct conversion.