Thanks for playin'!
The purpose of the switching is well explained on the game page. In case you missed it -
1. Path Choices influence the difficulty (easier in coward mode) and rewards (you may not get rewards in the coward mode unlike the brave mode to compensate for the ease of levels).
2. Visual Contrast by colour scheme inversion represents the paths to reflect that choice!
Variable jump height is a really good suggestion which I'll take note of! The game does give you increased jump heights as rewards in some "brave" stages.
We're aware of the spikes issues and will fix that. Thanks again for pointing this out!