I heard the PAP Trio at the recent Capital Audiofest and the speaker cables were the Fidelium cables. I have no idea if the internal wiring was also Fidelium, and even if it were the case, I would have no idea how tis affected the sound. All I can say is that the entire system at the show was one of the best I heard at the show. That being the case, the speaker cables had to be pretty good, at least in the context of this system.
If a speaker builder offers a cable upgrade, you can expect that the particular cable chosen works well with the speaker (at least in the mind of the builder). If you like the PAP sound overall, you can expect their choice of upgrade to be good. I have some experience with a local custom builder and have heard the difference the internal cabling choice makes as to the sound. One can easily hear the difference so it is quite important to upgrade to quality stuff. The particular builder likes Audio Note cabling and uses different cables in their lineup to tune the sound to the customer's particular taste. Even the choice of cabling to just one particular driver is something that matters. In one particular speaker, the chosen wiring was a cable that costs close to $20k for a stereo meter (to the midrange driver), but a less costly run of cable to the tweeter (cheaper cabling chosen because the builder actually tried the same ultra expensive cable but could not hear a difference when cheaper cables were substituted).
In short, I am saying that internal cabling matters quite a bit, so i expect the PAP people would be choosing the right cable to improve the sound of their own speakers.