Updating Generally & Updating Specifically 8 to 8.1

I need some guidance on what is/is not affected by updating. The help documentation and videos are ambiguous, imo good examples of information being provided by people who already know the answers and find it difficult to put themselves in the mindset of people who don’t. My points may seems obvious to tech people, but are not to me, and judging by the number of post-update-panic-posts in the forums, they are not to many other users too.
For me, upgrading to 8.0 went from the quick and easily hour set aside indicated by the video, to a weekend of my life I will never see again. I want to avoid the same again. By example in your docs it says “Once you activate a different theme, delete the Newspaper theme. Don’t worry, your content will not be lost.” The documentation also mentions code. But nowhere does it mention the effect on the hugely important and time consuming settings?

So i would appreciate it if you could clarify which of these headings will be affected by updating (and ideally any steps to be taken post update). I’ve started with the two I think I am clear on …

EFFECT OF UPDATING
Bespoke Code (including, but not necessarily limited to, anything entered into theme panel/custom code and theme panel/mobile theme/custom code): All will be overwritten. Must be copied out and re-applied.
Content (posts and pages): No effect, all will be retained.
Theme Panel Settings (all under header, footer, ads, layout and misc): ??? (if they are affected can the export/import settings tool be used – it states ‘to copy to another server’, and does not specify whether it would work between different theme versions. Is there anything not included in that settings export?
Mobile Theme: ???
Visual and TagDiv Pagebuilder elements used on posts & pages: ???
Demo Theme: ???
Licence key/activation: ???

METHOD OF UPDATING
in the documentation it gives alternative methods of updating, without any indication any are better than others. However i have noticed that in the forum when problems occur it is often stated that people should re-upgrade using the ftp method. does this indicate that the ftp method is more stable/reliable way of updating? I expect many of us will go for what appears the easiest method (wordpress) but if we knew ftp was a better way would jump through the extra hoops to do it that way.

I hope you can see that armed with that information I can see whether the benefits of an upgrade are worth the potential hassle, and also get a better idea of the realistic time it will take.

Thank you.