Yes, Walter you can change the section size, but since its set to 4 players by default, thats why most tournaments are 4 players per section. People don't worry too much about changing them.
As for which is best, well I guess thats personal choice. I like the 4 players per section because its a quicker tournament, and more chance of getting through to the second round. Higher number of players = more games, longer tourney and less chance of winning. But more of a challenge!