Well, this issue has been discussed for a while, and a solution has been found.

1. Groups of 8 are bad because they result in many games with no real motivation, and the group stage will last about 4 months. Moreover, in most groups, it will usually be clear who the favorite is, and in the second, more important part of the tournament, it becomes a lottery. In my opinion, this is bad on both sides.
2. Many groups of 4 people. The downside is that many groups will require additional games. Often, 3-4 people will score the same number of points.
3. The Olympic system is good in every way except for the certain randomness of the outcome, as well as the early elimination of tournament favorites. It is the fastest way to run a tournament.
4. The optimal options are double elimination and Swiss system.
In double elimination, EVERY game has motivation. This is how, for example, the Kalababa tournaments are held.

The Swiss system is also good; it has been tested many times on heroes.by. Both schemes allow participants to withdraw from the tournament without harming the overall intrigue if unforeseen circumstances arise. And most importantly, both options are second only to the Olympic system in terms of tournament duration.