Sorry, this is nonsense. You don’t seem to have understood the “basic facts” in the Wikipedia article.
The language of the Twelfth Amendment is substantially the same as that of the original clause [2.1.3] that it superseded, describing the electoral process for president and vice president. The only difference is that in the original scheme each elector was simply to vote for two candidates, without distinguishing their choices for president and vice president. The candidate receiving the most electoral votes would be elected president, with the second-most becoming vice president. When the elections of 1796 and 1800 showed this scheme to be unworkable, the Twelfth Amendment was enacted to separate the ballots for president and vice president instead of choosing both from the same ballot.
Both the original [2.1.3] and the superseding Twelfth Amendment specify that the electors are to meet “in their respective states”; there is no mention of their convening at a central Continental Congress.
The reason you “could not find how the electors were elected in the wiki article” is that the Constitution is silent on the subject except to say that “each state shall appoint [their electors] in such manner as the legislature thereof may direct.” The only role left to the federal Congress is to “determine the time of choosing the electors and the day on which they shall give their votes, which day shall be the same throughout the United States” [2.1.4]; the manner of appointing electors is left to each individual state, and different states may use different methods.
You are correct that the common practice initially was for the state legislature to appoint the electors directly; the use of an election by popular vote was a later development. In principle, there is nothing today to stop, say, the Arizona or Georgia or Wisconsin legislature from canceling their presidential election and appointing their electors themselves. It would cause a ferocious political firestorm, but they would be within their constitutional authority to do so. Whether they could do so retroactively, after holding an election and setting aside the results, is a different question.
In any case, there was never any intention for the electors from the several states to convene in one place to cast their ballots, and nothing in the original body of the Constitution or the Twelfth Amendment to prevent electors from exercising independent judgment in casting their votes. You are just flat-out wrong about that.
