These links should answer most of your questions. POE is a great feature, and a network cable means the highest quality image and availability, but it also means you have to cable each of your cameras back to your system vs wireless. Not saying that's a bad thing, just something for you to think about.

https://www.safety.com/surveillance-systems/#gref

https://www.pcmag.com/article2/0,2817,2475954,00.asp

If you don't have internet cable to each camera, then you will need a power cable for "wireless".

Not true, some are completely wireless, but need to be recharged regularly. Again, op needs to determine what is important to them,