The Chiefs came on to capture the Super Bowl last season. They are even better this year. 
Their defense has been solid since the middle of last season and the offense is even scarier with rookie Clyde Edwards-Helaire being an upgrade on their previous running backs. He's just one of two new players to Kansas City's formidable starting lineup. Having lineup and coaching continuity is vital this season. The Chiefs have that. 
The Chargers hold little home field advantage. Their offensive line is banged-up and quarterback Tyrod Taylor can't keep up with Patrick Mahomes. The Chargers have little back-door cover capability if falling behind by double-digits. The Chargers' O-line already is banged-up missing two starters last Sunday. Kansas City has the pass rushers with Chris Jones and Frank Clark to take advantage. 
The Chiefs put up 34 points on the Texans last Thursday. Kansas City's offense hasn't even rounded into top shape yet. The Chargers have a better defense than Houston, but losing star safety Derwin James hurts them. 
The Chiefs have dominated the Chargers beating them 11 of the last 12 times. Kansas City is just on a great point spread roll period going 10-1-1 ATS in its last 12 games. 
I'm not going to overthink this matchup. I'm just going to roll with the Chiefs.