I have looked over the thread. I'm not super comfortable because the posts relating to the single unit are pretty tentative and the stuff that seems like they have it all figured out is related to custom pcb for 4 units.
The PCB is one of the LAST things you would be doing. I'm getting the impression what you're looking for is more like a kit or someone telling you, "Do this and that and here's a PCB layout you can send in to someplace and they'll make you one, then just buy this list of items and solder them in place and flash the ESP32 with this command and it should work."
If that's what you want, you're not going to get it here. All of us here have spent a lot of time parsing what we've read here, learning things like how ESPHome works, and more. The first page of posts includes a Fritzing diagram of a system for one fan. From there, the next step would be using that, with the parts included, and wire, and a breadboard, to construct a circuit on the breadboard that matches the Fritzing diagram. From there, it's a matter of picking a way to connect to the fan. You can use the 4 pin to USB C connector some have used. Personally, I made the connections directly to a USB-C plug, and used that. No adaptor needed. (I did have to study USB-C pinouts to be sure I understood them and it's important to remember that normally USB operates on +5V, but that the USB line from the fan uses +10V.)
The PCB is pretty much the last thing to think about and shouldn't even be a concern until after you have a working system on a breadboard. I would also suggest a cheap oscilloscope to check the output before connecting it to your fan.
This scope is not at all high end, but, in the us, it's $47 on Amazon. You can use it to make sure you're getting a PWM with a duty cycle going from 0% to 100% as you change the settings on the ESP32 (which you can do through the webpage ESPHome automatically creates). You may not want to. While experimenting, I did blow out a fain, and they're something like $80-$95 (don't remember actual price). So getting a scope is cheaper than replacing a fan. (And, honestly, I didn't blow out my fan based on this, I dropped something and shorted out a connection and blew it out from carelessness when I was overtired.) In terms of the scope, it's about $40 less to get a scope than to replace a fan.
I would suggest:
Step 1: Learn how to compile the ESPHome configuration and get it uploaded to an ESP32.
Step 2: Get a cheap scope like I mentioned. Connect it to the proper output pin of the ESP32. Use the ESP32 web page controls to set the output and make sure the time in the duty cycle that the output is high is proportional to the value you pick for the pin output.
Step 3: Get a breadboard and wires and the components and build a test circuit using the diagrams and parts that was used on Page 1 of this thread. Again, use the scope to test the output from the MOSFET.
Step 4: Work out your connection to the fan. Either us the adapter others have used or do the research on USB-C connectors and find the proper connections on the USB connector to connect your circuit to the fan. Once that's worked out, try to test your output to make sure you're getting the PWM on the right pin.
Step 5: Connect it to your fan and test it.
Note that this is a general outline on how to do this. I'm not giving you specific steps and I'm not making an guarantees it'll work, or that you won't run into issues due to any skills or lack of skills you may have. In other words, as much as I'm working to guide you in the right direction, if you blow out your fan or damage anything else, it's NOT my responsibility.
As for the 4 unit PCB, again, DON'T THINK ABOUT THE PCB until you have a working circuit on the breadboard. I haven't done prototyping before, but I found a few changes I wanted to make from early on rather than go with the original designs here. (I think my first change was to a MOSFET wasn't on it's on micro-PCB.)
My first step was getting it working on a breadboard. Then I built a 2nd one to control my 2nd fan. Then I looked over what I had and realized adding a 2nd fan to the same system was easy - and, instead, added 3 more fans, so I could control 4 fans at once. The cost of the extra parts was, if I recall, less than $1 per additional fan, maybe less than $2 per additional fan. (I didn't post my 4 fan schematic.) I also added in a few diodes so my system draws its power from the fans themselves. The diodes make sure that the power supply doesn't feed back into the fans and so any fan can power it from any of the 4 USB-C plugs I'm using. (And I even sold my circuit design! Can't say anything about to whom or anything like that.)
There was atleast one post with circuit designs I ddn't understand for what seemed like multiple things all on the same drawing and piecing it together to make a unit to just plug into the usb-c comign off my fan, leech power to run and control the fan isn't something I can point out how to do on here with high confidence.
The issue is that pretty much everyone here has done a lot of work to make their system work. I came in with very little experience and pieced together a 1 fan control system and then expanded it from there. While we're willing to help and advice and share our experience, it sounds like what you want is a set of very specific instructions and a shopping list of parts. That's a big ask, since it means someone taking the time to prep that shopping list of parts and, honestly, you can get that from the posts on this thread. Most of that is at the start. Some of my posts, which are, I think, later in the thread, I do some summarizing behind the questions I'm asking. I try to do that to spell things out and so it helps me (and others, like you) follow what's going on and focus on the background of the questions I'm asking.
