For best results, the mics should be at least ear-width apart, and omnidirectional mics like yours can also sound excellent with much larger spacing. Experiment to find out which width you like best. It will depend on the environment in which you are recording and how far you are from the sound source. Instead of tape, you could try using a velcro strap to keep the cables from getting tangled.
If you decide to go with tape, electrical tape will work, but it leaves a sticky residue behind when you remove it. This is by design to seal out moisture from electrical connections, especially when there is bare wire to be protected. Gaffer tape is superior because it can be removed without leaving a sticky residue.