Much to learn you have....
Are you sure that it is truly
Cat5E wiring? Some systems use "proprietary" wiring and won't run a true POE IP camera. My neighbor just found that out with his old Zmodo system that looked like it had ethernet wiring.
Domes are not recommended outside unless it is well protected from the elements. The big issue is that the domes will hold onto water droplets much longer than other cameras and thus any dirt on it can then become problematic. And during a rain event with IR, the camera is basically blind...but even without rain, the reflections of lights even outside the field of view can throw weird reflections into the dome.
The domes attract lots of dust. Then rain. Then dirty rain spots. Glare from all angles of the sun. Then over time the sun will "fog" the dome like a car headlight.
We have more people coming here posting a problem picture at night thinking there is a problem with their dome camera when in reality it is the IR bounce from some object that the dome is then capturing and magnifying.
You need to be chasing sensor size, not MP.
To many people 4MP represents the best overall sweet spot.
Keep in mind the good 4K cameras need to be on 1/1.2" sensors and those cameras are only good for OVERVIEW purposes or IDENTIFY within 15 feet or so of the camera. These cameras are not like Hollywood where you can digital zoom, at least not very much and not at night.
Further, these 4K cameras demonstrate that these types of cameras are not infinity focus and they have a small focus range of about 15-18 feet and anything shorter or longer than that distance will be soft/blurry.
It is not recommended to buy kit/complete system, but rather to purchase each camera for the goal of that camera.
Almost every big box store, consumer grade cameras and all-in-one-box kits come with either 2.8mm or 3.6mm cameras. I started with the four 2.8mm camera box kit system and I was like "I can place one on each corner of the house and see my whole property and the whole neighborhood." A newbie loves the wide angle "I can see the whole neighborhood" of the 2.8mm fixed wide angle lens. I LOVED IT WHEN I PUT IT UP. I could see everything that would be blocked looking out the windows.
It is easy to get lured in to thinking the wide angle "see the whole neighborhood" because you are watching it and you see a neighbor go by and you are like "Look at that I can tell that is Heather out walking." and "Yeah I can tell our neighbor 4 down just passed by". Or you watch back the video of you walking around and are like "yeah I can tell that is me".
Little do we realize how much WE can identify a known person just by hair style, clothing, walking pace, gait, etc.
Then one day the door checker comes by. Total stranger. Totally useless video other than what time the door checking happened.
Then you realize that this wide-angle see the whole neighborhood comes at a cost and that cost is not being able to IDENTIFY who did it. These 2.8mm wide angle cameras are great overview cameras or to IDENTIFY someone within 10 feet of the camera. At 40 feet out you need a different camera.
See this thread for the commonly recommended cameras (along with Amazon links) based on distance to IDENTIFY that represent the overall best value in terms of price and performance day and night.
The Importance of Focal Length over MP in camera selection
It is recommended to buy one varifocal like the 5442-ZE (54IR-ZE) and play and learn from it and then buy cameras to meet your need for each location.
