If all the Weights on the wheel are set to 1, the odds won't change. But if some slices have different Weights, they can change.
For example, suppose you choose the "Shift" effect, and set "Win" to a Weight of 1 and "Lose" to a Weight of 999.
In this case, without any effect, "Lose" would almost always be chosen. But when the Shift effect occurs, the result shifts by one slice, so in most cases "Win" ends up being chosen instead.
This means the wheel first draws a result based on the normal Weights, and then the effect's probability and the way it shifts can change the final result.
If you want the wheel to spin strictly according to the odds, simply set all Weights to 1 and the odds won't change. Please rest assured.