The bets are determined by checking a wide variety of projections against my own knowledge of how players will be utilized given game context. The player prop lines were taken from this site.
When analyzing projections from fantasy sites, you'll often find that the projections are higher than betting lines, which will make you bet shit tons of overs. This is a common mistake. The projections are mean based, while the betting lines are median. Mean projections tend to skew higher because the range of outcomes are not evenly distributed. (i.e., a running back on a good day could go for over 100 yards, but he would never go under 0... hopefully). If you find a mean projection lower than the Vegas line, the under is likely a good bet. To bet an over, the mean projection should be significantly higher. All bets below will follow that logic.
Sunday 1PM Slate
Matt Stafford o195.5 passing yards -110 (Bet365)
Matt Stafford o18.5 completions -115 (Bet365)
Bryce Young o178.5 passing yards -101 (Caesars)
Keaton Mitchell u45.5 rushing yards -105 (PointBet)
Khalil Herbert o21.5 rushing yards +105 (Bet365)
Ja'Marr Chase o67.5 receiving yards -110 (DraftKings)
Chris Godwin u49.5 receiving yards -104 (Caesars)
Amon-Ra St. Brown o6.5 receptions -105 (DraftKings)
Sunday Night Football
Dak Prescott u301.5 passing yards -110 (Bet365)
Tony Pollard o58.5 rushing yards -106 (Caesars)
Monday Night Football
Tommy DeVito o169.5 passing yards -110 (Bet365)
Tua Tagovailoa u290.5 passing yards -120 (PointBet)