I see you decided to go with walk-in!
I do think you will look back and be glad you decided to do this. I see everyone has given you some great suggestions, so...get that coop ready!!!
If I remember correctly you wanted chickens for a reason similar to "pets with benefits". Now for some FUN STUFF!!
IMO a walk-in made it easier for me to brood in the coop. I had room to make a corral to block off an area to keep them out of the corners for a couple of weeks. I also had room to take a small stool inside and just sit with them. This helped us all to get used to each other. After a couple of weeks I took out the corral, blocked off the nests and let them have free reign of the coop, they explored every nook and cranny and made themselves at home. I also let them out to the run at about 3wks. (summertime), I could take my stool or a chair in there, walk around and let them just be growing chicks ~ chasing bugs, taking a dust bath, they would come up and interact with me. When it's warm I still like to take a chair and sit with them in the run. Some want to sit on my knee, others just want to be close but not held, but they all want some type of interaction. They do talk to you and I think you will get a kick out of them.
I always wanted chickens, but I just didn't know how much joy and fun they could bring.
@aart has a good article on brooding without a heat lamp
Can't forget @Blooie and her mama heating pad