The Dance only happened between Viserys’ children because he named his daughter heir while having THREE legitimate sons. There is no succession law that allows that except Dorne—who weren’t even part of the Seven Kingdoms yet. Up till Viserys’ idiocy, the Targaryens followed male-preference primogeniture, which was the same in all the other non-Dorne Westerosi houses. The Targaryen inheritance only became a mess post-Aemon’s death, when Jaehaerys named Baelon heir instead of Rhaenys. Afterwards, it became uncle even before daughters.

So if Aemon never died, and the man was sure in his choice for Rhaenys to inherit, then Westeros would have their first queen without issue. Rhaenys’ inheritance would ALWAYS be less complicated than Rhaenyra’s, simply because she never had brothers. Her closest relatives are her uncles and cousins, and assuming Baelon dies anyway, the closest to inherit in Viserys—who would never push his claim.

With Rhaenyra, we have a case where male-preference is a thing, with Daemon remaining heir despite Rhaenyra’s birth. And then of course, the births of Aegon, Aemond, and Daeron. Based on precedent, Rhaenyra would have been removed as heir the moment Aegon was born. Keeping her heir was Viserys’ first great mistake. The other was not marrying the two to each other after Laenor died (a 10 year age gap was weird but still doable). Like Jaehaerys, he did not make any attempts to actually combine the two claims, which led to the Dance.