If you look at the last eight years, you'll see that BOTH teams gave the other team several opportunities to win.
In 2011, and 2015, BYU turned the ball over multiple times- and Utah was able to exploit those turnovers into points.
In 2016, Utah turned the ball over six times, and yet they failed to capitalize on most of them, and lost on the failed 2-point-conversion.
As someone who has attended both schools, and loves college football, I will be watching and cheering for both teams this year. However, most people know my ultimate loyalty lies with Utah. As a Ute, I'd be lying if I said I wasn't at least a little nervous. Last year, Utah's offense didn't fully fire on all cylinders until Stanford- the 6th (?) game of the season. Aside from 2015, when Utah hosted Michigan, they have largely started out by playing cream-puffs in Week 1, and even in those games, they haven't looked great.
I'm not sure if there is a rivalry in CFB like BYU/Utah. I don't know of many major rivalries in which one team is a P5 team, and the other is not. (Notre Dame isn't technically a P5 team, but they are still among the Top-5 All-Time programs.) Despite Utah's advantage- in recruiting, depth, and money- I still believe that BYU is still very talented, and capable of beating Utah.
To me, it isn't about "If both teams play their best...". It doesn't work that way. If it did, we could just count the number of stars, and just declare either Alabama or Clemson the champ right now.
To me, it's about which team can make the fewest mistakes. And when the other team does make a mistake- can they take advantage. In 2015, 2016, and 2018, BYU threw at least one pick-six. They can't afford to do that. If they can take care of the ball, however, and exploit Utah's mistakes, this could very well be the year that BYU breaks the streak.