Not every day you see plain straight up Serb ultranationalist talking points in discourse, but I suppose there has to be a first for everything. Seconding thanks to
@CalBear for prompt remediation.
I definitely agree with North Macedonia's postwar settlement being a tenuous issue, not in the least because a partition of the prewar territory is already agreed on in some capacity - the cession of Monastir/Bitola to Greece. I have a really hard time seeing Serbia/Yugoslavia being able to renege on that deal given how much political influence Greece has over the very survival of the Karađorđević regime, so the question then becomes one of how far north you draw the lime, and whether any other pieces of southern North Macedonia get traded in; obviously both Greece and Serbia will want to maximize their control over the Ohrid area, so there is room for additional contention beyond the minimum agreed trade. So that question is already going to put a bit of strain between postwar Serbia-Montenegro and Greece, even if only to a degree muted by prior agreement.
With respect to Bulgaria and its claims (and the issue of how a Serb nationalist state is going to treat a populace associating with a distinct/rival South Slavic identity), I was wondering if a token re-cession of the Strumica area (the southeastern part of the region controlled by Bulgaria between the Balkan Wars and end-WWI) might be agreed upon in a bid to "decisively settle the issue," restoring the border set before the World Wars and very slightly compensating Bulgaria for losses to Greece while in practice changing little on the map. It's a very small change, but I can see it offered by the government in Belgrade if they feel buying some credit with Bulgaria is better than them cutting bread with either the Greeks or Eastern Bloc (inc. Tito's partisans). Besides that single option I can't really think of any concessions Serbia would feel like making territorially, and in terms of regional Slavo-Macedonian/Bulgarian identity I have a hard time seeing Chetnik Serbia doing anything besides heavy handed assimilation and/or deportation tactics. The Albanians in the region are in a similar pickle I fear, barring some unforeseen watershed success for one of the Albanian partisan factions.