There are now three different levels of American football you can bet on: the National Football League (NFL), college football (NCAA), and the newly-formed Alliance of American Football (AAF). The NFL is the top professional league in the world, while college (university) is the level for players 18-23, which are not yet professional. The AAF is a new venture for players that are either trying to make the NFL, or get back into it, but it is professional.
The NFL has 32 teams, and is despite the records of the teams at the top and bottom, the difference between the teams is very close. In college football, with 130 teams, there are often matchups that can allow you to find an edge.
For instance, one of the surprise teams of the last two seasons in college football season has been the Army Golden Knights. One of the service academies. Army has found a way to implement an offense that not many other teams run, and is very hard to play against with just one week of scouting. The Golden Knights have gone 23-5 in 2017-18, led by a devastating offensive attack. Army scored more than 30 points seven times, including a 70-14 win in the bowl game over Houston. Many college games see much less action than an average NFL game, which can be an advantage to a bettor.
As far as NFL betting, some of the better ways to neutralize the high money lines would be to put two or three big favorites into a parlay. NFL favorites in 2018 went 175-90-2 straight up (with the money line, ie. no point spread), good for a 66.04 winning percentage. That percentage went up to 69 when you bet home favorites (123-55), by far better odds than betting any of the spread lines.