There are roughly 120 teams in the top division of college football, and unless that amount of teams is sufficiently paired down, 4 teams isn't enough statistical representation to determine a true champion. 8 team playoff means that less than 10% of teams even make the playoffs for a CHANCE to play for the championship in the playoffs. That is still by far the lowest playoff percentage of any sport in history. If the top 10% of your teams aren't "deserving" of playing for the national championship, then there are fundamental flaws in your sport so great that it should be completely disbanded and you need to reorganize from scratch. 8 team CFB playoffs is equivalent to the NFL starting their playoffs with the Super Bowl.
Now even in an 8 team playoff, how the teams are picked still matters, and I'm worried college football is going to really dick this up by giving conference champions autobids. In a system with round robin play for conference championships, this would actually be a good way to objectively pick playoff teams... but that's not the system we have. We have mong conference champion games where conferences are further subdivided to divisions. This means that every year some borderline .500 team will back into a conference championship game because the system is flawed (there is always a weak division somewhere). Then that team actually wins their conference championship game and makes the playoffs with a .500 record over teams that actually "deserve" it more. This "small division" issue is the same thing that fucks with the NFL
Anyway, here is how you perfectly split up a sport that has hundreds of teams (promotion/relegation talk inbound! @zeek)
Split the Power 5 Conferences (do some wheeling and dealing to exclude the shit teams and bring in the best of the mid majors) into 5 geographic 10 team conferences (3 southern conferences 2 northern conferences). Take the next 50 teams and do the same thing with them. Take the remaining 20 teams and add them to the best 30 FCS teams. Etc etc on down the line. Basically we are organizing all college athletics in segments of 50 in these 5 distinct geographical regions. The regions are "fuzzy" in that the boundaries move to keep the conferences as geographically close as possible.
At each level the conference plays a 9 game round robin conference schedule + 4 random games against the closest adjacent conferences (9+4 = 13 games total) conference champions are based on total record, not just conference record, with tie breakers being objective. The conference champions and the next 3 best record "wild card" teams (with objective tie breakers) make the 8 team playoff. With this setup, every playoff contender will be deserving. The championship teams will play a total of 15 games, just like now under the 4 team playoff with the mong conference championship games.
At the top level this is self explanatory and there is no added benefit other than playing for the championship. At the lower levels the teams are playing for the playoffs AND to get autopromotion to the upper division. The lowest performing teams 8 teams in the upper division (5 conference losers + 3 wild losers) would be autorelegated. You could also tweak this setup to add promotion/relegation playoffs, but I don't really like rewarding under performing upper division teams with an additional "out."
Each year the conferences would be re-shuffled based on the geographic locations of the remaining 50 teams.
Edit: Fixed %, thanks for pointing that out Redmond, the point is the same.