1. Michael Penix Jr. must start
It doesn't matter that Kirk Cousins is under contract next season at a high rate. The quarterback has fallen off a cliff and showing no signs of being able to get off the mat. Yes, the job was Kirk's for the next two seasons based on the contract if he simply played at an above average level. Even playing at a league average level would make it close to impossible to get Penix into the starting lineup.
However, the quarterback has thrown eight interceptions and not a single touchdown during a season-defining losing streak. Barring the Falcons going on a shocking run to close the season it is time to close the book on Kirk Cousins. You whiffed on the signing and it is time to pay the price and allow Penix the chance to win the job.
That doesn't mean you have to cut Cousins but bring in both quarterbacks and have a serious competition. One that allows you to evaluate the young quarterback and have a backup plan. Unless Cousins is injured and playing through it there isn't a reason to consider putting him back into the lineup. Penix should be given a chance to start.