In answer to questions: 1) Yes, the Constitution gives state legislatures great discretion in the appointment of electors. 2) In PA, the legislature used that discretion to provide the governor with authority to appoint electors after certification. Continued...
3) If @dougmastriano's resolution passes, it would take back the power the PA legislature has delegated to the executive branch (governor). In essence, the PA legislature would become responsible for the appointment again.
4) This, of course, would open the door for the PA legislature to deem the election fraudulent and only appoint a slate of Trump-faithful electors. 5) There are many unanswered questions, but suffice to say that if the resolution passes, we're in for a wild ride!