Sometimes life happens and things take somewhat longer than anticipated!
Hence the corresponding blog to this thread is still imminently forthcoming...
Since my previous response on this thread I have been refining 2 of the 3 primary Flows I've created for my demo app more generic to accommodate a far wider use case scenarios. Those are now basically complete now and I by and large just need to describe what each step in each of the Flows does in my upcoming blog.
Equally I have enhanced the initial demo app I created to showcase what I at least think is quite an awesome user experience rendering content the user has permission stored in ANY site (and subsites) from ANY Document Library (and subfolders) or List.
In my app I also demonstrate on-the-fly conversions of Word, PowerPoint, HTML and likely others I haven't tested can instantly be converted to PDFs and displayed in a PDF Viewer control and equally just as easily view actual PDF documents stored in a SharePoint document library in that same PDF Viewer control with zero effort or workarounds that have historically been required in order to view PDF documents stored in SharePoint due to authentication related challenges.
Notwithstanding the demo now showcases how calling a single Flow content from any list on any site can be consumed by the app inclusive of ALL the metadata pertaining to whichever list you query, which thereafter be displayed in a Gallery control or any other requirement for your app. Furthermore the same Flow returns the actual schema definition for the list, such that at run time the app is able to determine the field type for each column in that list for example which columns are lookup fields to another list on the site, person or group fields, date time fields, text fields with the number of lines and maximum length, choice fields inclusive of possible choices for that column as well as attachments etc.
I have recorded a new video of the demo app I have created. I am currently reworking the Flows to remove some unnecessary complexities rather than try and explain in the upcoming blog what the initial intention of those "now" unnecessary steps were intended for.
Demo of v2 of the app on YouTube:
PowerApps SharePoint User Experience Demo v2
On a side note, everything in the video recording I uploaded has been implemented in a single screen in the demo PowerApp showcased in the video. Surprisingly enough I found it easier to develop the demo app with all the functionality depicted on one screen, go figure 
