Dear CJGT,
You can create a folder content type with the specific site columns on the site.
If you are the site owner, you can go to Site Settings(Site Information>View all site settings)>Site columns under Web Designer Galleries>create the site columns such as foldercolumn1 and foldercolumn2.
Create a site content type (folder content type)>Site content types under Web Designer Galleries>create a site content type such as foldercontenttypeA and add the site columns foldercolumn1 and foldercolumn2 to it.
Now the site columns are limited to the folder content type foldercontenttypeA not other content types such as files.

.
You can create a view such as FolderView showing files and folders with the folder content type columns and set the file-only view scope on the default All Documents view via Rest API and Power Automate.
In the demo, Rest API calls are the following.



.
FolderView:
Uri: _api/web/lists/getByTitle('library1')/views/getByTitle('FolderView')
Method:POST
Headers:
{
"Accept": "application/json;odata=verbose",
"Content-Type": "application/json;odata=verbose",
"IF-MATCH": "\*",
"X-HTTP-Method": "PATCH"
}
Body:
{
'\_\_metadata': {
'type': 'SP.View'
},
'Scope': 2
}
All Documents:
Uri: _api/web/lists/getByTitle('library1')/views/getByTitle('All Documents')
Method: POST
Headers:
{
"Accept": "application/json;odata=verbose",
"Content-Type": "application/json;odata=verbose",
"IF-MATCH": "\*",
"X-HTTP-Method": "PATCH"
}
Body:
{
'\_\_metadata': {
'type': 'SP.View'
},
'Scope': 3
}
Result:


.
In FolderView, folders appear and you cna see foldercolumn1 and foldercolumn2 appear and these column values are limited to foldercontenttypeA.
In All Documents, folders disappear and only files appear and the foldercontenttypeA columns disappear.
Hope that the information above helps you and have a nice day!
Thank you for your effort and time.
Sincerely
Cliff | Microsoft Community Moderator