Thanks for your reply. I have studied the cliff notes 
Why did you recommend the IPC-T54IR-ZE-S3?
What about the IPC-Color4K-T 8MP? This one has a larger sensor (1/1.2" to 1/1.8") and LED illumination. Is there something against this model?
I have mentioned, that I would I would like to have two way talking. The only suitable turret cam I found is a Dahua. The IPC-HDW3849H-AS-PV has this feature but the sensor seems to be a little bit small (1/2.8"). What do you think about the red an blue LEDs on the Dahua. Does it makes sense or is it just a useless gimmick?
The 4K-T camera makes a great OVERVIEW camera, but it has a very narrow focus depth of 15-18 feet, so anything shorter or longer than that distance will be soft/blurry.
So the ZE is still the king of the hill and the most versatile. The S3 chipset works very well in low light. And you can adjust the focus to fit your field of view.
You will find that the two-way audio is walkie talkie like and most here do not use it. You press the mic button and talk and then let go so you can hear the next person. And there is a several second lag. Most of us with two-way audio never use it outside of the initial play period with it. Or to send an audio alarm.
One of those things that in theory sounds good, but reality it just doesn't cut it for a conversation. Works good to yell "get off my lawn" but to have a conversation, forget it.
The 3849 is a horrible camera that should have never been sold.
This is active deterrence camera on an 8MP on a
1/2.8" sensor, so it is on a horrible MP/sensor ratio. You cannot have enough light at night for it to perform well. That sensor is designed for 2MP so a 2MP camera will kick its butt all night long.
Even worse, since this 8MP is on the same sensor and CPU as a 2MP non TIOC camera and there are many threads here showing how under-performing that 3849 is. They had to limit bitrate and other parameters on the 3849 to try to make it functional, and it just doesn't cut it.
In my opinion the 3849 should not be sold with that current MP/sensor and CPU combination, but alas everybody wants 4k and chases MP over sensor and this camera is the epitome of that thinking.
Further, the red/blue flashing lights are more gimmicky and are certainly not a deterrent. With any ambient light you won't see the red/blue flashing unless you are looking right at the camera.
If you want active deterrence, your best bet is to go with the 2MP IPC-T5241H-AS-PV that will blink the white light. This is on the ideal MP/sensor ratio and will perform comparably to any similar 2MP fixed lens camera by Dahua. I have two of them. I have some of the other active deterrence cams as well, and would opt for the 2MP in every instance except for indoor, one could go with the IPC-HDW3449HP-AS-PV that has the red/blue lights that will bounce off the walls and be much more impressive than outside.
Lot's of threads here where people showed how bad the 3849 camera is in performing:
IPC-HDW3849H-AS-PV issues
IPC-HDW3849H-AS-PV loses connection/reboots during the day
Replaced HDW5442TMP-ASE by HFW3849T1P
Dahua 8mp (TIOC): Full Colour, Active Deterrence & AI
IPC-HDW3849H-AS-PV Video Quality