What you are explaining here is the longest chain, without the word valid. While the longest chain is usually valid, it's not necessarily so. Validity is decided by the nodes which are the economic majority. Miners are incentivized to follow the economic majority, but they are not required to do so.
I don't think that's how it works at present. As I understand it, the longest chain is decided by the software, the user has no way to determine which chain the software follows. Might be wrong, but it's a debugging feature if it exists at all.
There is no such thing as "the software". This concept is inoperative, because every node potentially runs different software, e.g. different software bases, different software versions, node specific configurations or patches, or in some cases different operating system and network environments which determine how the software behaves.