Is it fine to bunch together power wires?

Hi,
best is to keep them separated but if not possible arrange them in away that crosss each other.

What pet said. 

Hi,
best way to keep them seperated or if not possible try to make the cross each other.

I avoid that.  

The biggest issue occurs when cables run parallel to each other. Crossing is not so bad, particularly at right angles. You are better off having a jumbled mess than having all the cables neatly organized running parallel, even if they are spaced a 1/2" apart. The amount of current that is induced in the neighboring cable is dependent on how much current is running through each cable, how close together they are, and for what distance. Having cables occasionally cross each other will result in a lot less induced current than running them parallel in close proximity for more than a very short distance.