When they're talking about "growers" and all this daylight exposure stuff, they may be referring to meat birds. I don't know anything about that, and whether that would be good advice or not.
For your basic regular backyard chickens, you're supposed to start around 95 degrees. We use a red heat light. Supplemental light just comes from windows, we don't leave any other light on at night. We used a white heat light the first week we had chicks and of course had to leave it on to keep them warm. Man, those chicks were loud. Probably because they couldn't get any sleep! Then we went and got a red one.
Some here like the reptile warmers (heat only, no light) but I have not seen or tried one.
Use the 95 degrees as a beginning estimate, lay a cheap thermometer down on the floor of the brooder and use it to get the heat just about right. From there, just watch the chicks. If they're all huddled together under the lamp, they're cold. If they're as far from the light as they can get, they're hot.
Chicks can definitely handle much cooler temps as long as they have somewhere warm to go. I have learned to think of the heat lamp area as equivalent to running back under mama's feathers for a warmup or to sleep. The rest of our brooding room in the coop is much cooler, but they have that heat source to run back to. Do not try to make your whole brooder 95 degrees. More space is better so they can find a comfortable temp for themselves.
Do not freak out, I was exactly where you are four years ago, reading everything I could get my hands on and worrying that I would do something wrong.
Oh, and
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