The overall theme is what you’re doing now which is to do research and ask questions. Once you have narrowed down what your real world needs are.
Sit down and really consider the budget as this will dictate what you have and most times reflects the final quality you obtain from all the hardware.
There are just some things you shouldn’t skimp on and that is the wiring infrastructure. So only buy named brand certified in wall rated (CMR) CAT-6 (23 AWG) solid copper wiring and not CCA wire.
Copper Clad Aluminum (CCA) cable is illegal to use in walls per the NEC / CEC and does not have the same current carrying ability as pure copper nor is it fire rated.
Run multiple pairs in hard to reach areas and consider pulling 22-4, 18-2, 16-4 in wall rated cable. As this will allow you to power anything from LV lights, speakers, microphone, IR etc.
Do not fall prey to the latest fad of powering high current things with CAT cable! No matter how good the cable is it’s not the equivalent to a properly sized cable for X vs Y as noted up above.
You can’t be using 22-4 cable where 14-2 Romex is required! As you literally see this happening in this forum and others because people are cheap and ignorant as to what ampacity is allowed on X cable.
This leads to another major Do Not, Shall Not, Ever power multiple items off a single CAT cable.
This doesn’t mean a microphone or a very low power speaker.
You’ll see people literally power 2-4-6 IP cameras off a single line?!?
Not only is this against every industry standard or norm it’s not common sense!
It’s done out of convenience and not understanding a failure & fire is just waiting to happen. Every cable is de-rated to allow headroom. Generally speaking it’s 80% of its ampacity as this allows other factors like heat which increases resistance or the worst in extreme cold less resistance and more current will flow.
Many people also fail to understand one of the major reasons failures and fires are created as it pertains to electronics. The vast majority of electronics like CCTV cameras use highly regulated power supplies that allow them to operate in a wide voltage range.
This is where people mistaken Ohms Law. Because when I tell them when voltage drops current rises the literal Ohms Law folks can’t understand how that can be?!?
That happens because that highly regulated devices tries to keep operating even when the voltage drops to 9 VDC vs it’s standard 12.X VDC! Almost every camera shows a tolerance of 25% variance. That literally means it will run just fine at 15 vs 9 and just great at 12 VDC!
But what they don’t tell you is current will increase because the electronics at some point crosses over to a danger point and tries to it buck up.
So now imagine you have 4 cameras all being powered by a single cable pulling X amps?? Equipment will fail prematurely, cable will open up, wire will heat up.
Other things to consider is proper routing and securing cable. Obviously the shortest path makes sense but sometimes a longer run is needed because it’s just safer and provides better access and long term maintenance if required. Wiring should be secured and supported at least every 4 feet and not left laying on insulation, OSB, etc.
Always leave enough service loop to allow you to move or re-terminate at both ends. All cable should be marked with a sharpie, tagged with wire tape. When pulling cable or protecting the same with 3M 33 speed tape follow the creed: Be a friend & Leave a end on the end of the tape for easier removal.
In the ideal world all wire runs should be the same length as this allows you to calculate and know the resistance / voltage drop. Then if you just have to run multiple items on a single wire you’ll know if you’re still within the 80% vs 100% maximum!
In the worst case scenario document what each length is so you know. Name brand wire will be marked for length. You’ll never see the same on cheaper cable.
If you live in a highly regulated area where the inspector checks everything. Insure all cable shows all the required safety markings otherwise you’ll be pulling it out!
Been there done that in hundreds of homes and businesses over the years.
It goes without saying plan out where you believe a camera would be ideal. When you’re in the attic, crawl space, basement reality hits as to how easy vs hard it will be to run cable. As is pointed in the excellent
WiKi build a test rig and test a single camera to learn the ins & outs of the hardware.
But more importantly the limitations of what that specific camera is able to see and capture in both day & night. Trying to balance spot view, over head, perimeter, and panning views takes time, money, and good planning.
When new hardware arrives always set it up on the bench. Perform a solid one week burn in as any infant mortality will show itself normally during that period.
Lots more to discuss but do a search on this forum as there are thousands of posts that offer a gold mine of knowledge from some of the smartest and talented people in DIY / Pro!
Cheers from Canada
Not only is this against every industry standard or norm it’s not common sense! 
