I went down the route of building my chicken coop and run before I got my chickens. I did not want to build two coops so I took quite a while to design the coop before building it. Even with all of my research, there are a couple of things that I would tweak BUT the coop functions well as is.
I am not a builder and my chicken coop was my first BIG construction project. I did not buy plans but I did end up watching a bunch of videos and looked at free design plans to get a feel on how I wanted my coop to work.
My recommendation is to not build to minimal standards but rather plan to build a place for the number you are thinking of. I don't know if you have heard of chicken math before but by golly is it true!
The things that I would recommend not to lose sight of are the location and amount of ventilation you will have in your coop, what kind of bedding system you are going to use (Deep bedding will need some depth built in but poop boards would avoid the need) and having sufficient perch space.
I'm sure if you posted your ideas and asked for feedback, a bunch of folks here would assist you in your planning so you can just build once.