Your not paranoid, well at least not fully
Bad cable management can defiantly interfere with the ability to disperse heat inside your case, and can lead to loss of performance. Best thing to do is try to zip-tie your cables together in bunches, and then zip-tie those to a spot in your case out of the way. Just be careful not to pull on them, or place them in the way of any fans.
Oh, and make sure your computer is off and un-plugged when doing this.