Placement and cabling determine whether footage is actually useful — and there are legal limits on where cameras may point.
Most disappointing camera installations are not equipment failures. They are placement failures: cameras too high to identify faces, pointed into sunrise glare, or covering an area nobody cares about.
PoE (Power over Ethernet) carries power and data over one cable, is far more reliable, and is the right answer wherever a cable can be run. Wireless cameras still need power, so the only saving is the data cable; they are appropriate for locations a cable genuinely cannot reach. Battery cameras are convenient and involve ongoing recharging, plus a delay on wake that can miss the event.
Decide retention before choosing storage. Continuous recording on several 4K cameras consumes storage quickly; motion-triggered recording extends it considerably at the risk of missing pre-event context. Many systems record continuously at low resolution and switch to high on motion, which is a reasonable compromise.
Rules vary by state and municipality, and this is not legal advice. Broadly, in the US: recording your own property is generally permitted; pointing a camera into a neighbour's window, yard or another area with a reasonable expectation of privacy generally is not. Audio recording is treated far more strictly than video — many states require consent from all parties, so recording conversations can be an offence even where the video is lawful. Many systems ship with audio enabled by default; check that setting. For rental or shared property, and for any workplace installation, check the specific rules that apply before installing.