Create new door with nested door swing

[vince.lam]

Hi All
First of all, I am an absolute beginner of Revit. I followed some online tutorial on how to create your own internal door (pretty much I want to create my own custom door for a project I am doing for the company).
the link is here: https://revitpure.com/blog/17-steps-...swing-in-revit

Here are the detailed steps on what I have done:
I used the metric door template and successfully created the door frame using "rough dimensions" (Structural dimensions - takes me ages to figure out what the hell is rough dimensions). My first question is, why do you create the door first and then set the structural opening dimensions? So say, for example, I want a structural opening of 910 x 2100mm, I have to create an opening of 826 x 2040mm? Am I correct? The tutorial using formula to generate the structural opening. Again, It said the structural opening is the =Width-(Frame thickness*2-(difference between frame and structural opening width))? of which the frame thickness is the width of the architrave.
The formula on its own doesn't make sense at all. I have to re-figure out a formula so the structural opening and door leaf will be what it will be. Am I doing anything wrong?

Then I created another family file on the swing. Everything is fine here, but once I created and saved the file called "door swing". When I load the door swing into the frame family. I will show under the families in the project browser but not on the project. I right clicked on the door swing under the families and create instance, but it will only shown on elevations, but not plan view. How do I fixed that? I haven't even got to the point of nesting the swing to the door frame yet.

Please find attachments of the door frame.rfa and door swing.rfa on what I have done so far. Hope that helps.

Update: I have now sorted the door swing to frame family problem. It happened to be me being stupid when creating using the Metric Generic model, it automatically opens quite a few views, and I used the wrong one from the start. Hence when inserting the door swing to the frame family. It will always be on the elevation.
Now I have created a basic door with openable swings. (ie. I can specify the angle shown on project and on selection box (3d)

I am using Revit 2021.
Vincent