What are the effects of cable ties?

Ckoffend probably has the best answer. If you're worried about the metal wire in some twist or cable ties, use entirely plastic ones.
Even the plastic hoops you buy from garden shops to hold a plant to it's stake will do the job, and cost next to nothing.

While cable ties may be more convenient, I would be more apt to use zip ties. You can even buy zip tie mounting plates that are made of plastic that have a peel and stick silicon release liner (ie. sticker like) that will allow you locate and even support the cables where you want them (ie. more out of site). The zip ties can be purchased anywhere, the plastic mounting plates can be purchased at a local industrial electrical part store/distributor.

Indeed, most cables are shielded these days so there is no worry. Twisting them won't help if they are well shielded to begin with. Check to see with your cable manufacturer if you aren't sure about their shield quality.

Now if they aren't shielded, a rat's nest is the best solution, believe it or not. You certainly don't want to coil the slack up, nor twist tie them together in parallel.

Arthur

As long as the cables are shielded, both audio & video, you can use cable ties all day long. Don't over tighten.

When you use the ties on the left channel, twist them to the right and when you use them on the right channel, twist them to the left. This preserves polarity and prevents smearing. At least that's what I noticed in my system.