So, time for some facts I think.
Without komi, if both players played flawlessly under Chinese rules and the game does not contain seki, the ending position must distribute 361 points between the two players. Since both players are perfect, you would want the komi to be such that if they swapped colours, the result would be the same (i.e.: under perfect circumstances, the game would be purely testing the skill of the players, which should be equal). This means that Chinese komi should be an odd integer, or else the 361+komi points are unevenly distributed.
We aren’t perfect players, but we do have a large record of games that have been played. Statistical evidence shows that komi should be around 7 for these games. What is not being accounted for, is that players might play safer if they are ahead, and therefore win with a smaller margin than if the komi was different. Another thing that is not taken into account, is whether the statistical difference in score accurately reflects the “perfect komi” value or if it is skewed in favour of one of the colours (perhaps for us ‘simple humans / computers’ it is easier to play black than it is for the perfect player). Actually the human komi doesn’t even have to be an integer.
So the result is that we can estimate 7 to be the correct komi (hence 6.5 in the Japanese rules and 7.5 in the Chinese, and most of the other komi also are such that they are close to 7), but we don’t have a way to be certain that it is the right amount to be “perfectly” fair. It is statistically fair, though.
The question about whether you allow tie-breakers does not really have much to do with what the perfect komi is, and just depends on the rules that the players agree on before playing. If you absolutely want to avoid this, you could use something like the pie rule (where the first player plays the first black stone, and the second player chooses which colour he plays with) or things like betting on the komi. Both of those are fair ways to play without any of the players feeling he has a disadvantage.