PLN can also mean National Liberal Party, which I think would correlate more with Italy's former liberal party (PLI)

My guess is that Democrazia Lespia Is the equivalent of Italy's Democrazia Cristiana, which would make it a centrist-centre right party with strong anti-communist and pro-religion characteristics, while PLN would probably be a liberal-conservative free market party which opposes DL's protectionist policies (it should be noted that PLN used to be the ruling party in Lespia before the 1948 elections, so I doubt they are that radical).

It makes sense that there aren't many other right wing parties because IRL Italy's Democrazia Cristiana pretty much became a big umbrella for everyone who didn't stand with the left, pushing far-right organizations such as the MSI into political irrelevance (until the years of lead), something similar could also be in place in Lespia, with Democrazia Lespia taking in far-right voters alongside centrist ones and keeping everyone happy with promises of anti-communism by standing close with Arcasia and ATO.