Smart Switch backs up the following:
Contacts
SMS Messages
Call logs
Photos - bmp, wbmp, gif, jpg, jpeg, png, tif, tiff
Videos - mpg, mpeg, avi, divx, svi, wmv, asf, pyv, mp4, m4v, 3gp, rm, rmvb, mov, mkv, skm, k3g, flv, swf
Music - mp3, wma, wav, pya, ogg, m4a, aac, 3ga, flac, smp, dcf, mid, midi, amr, qcp, imy
Documents - pdf, ppt, doc, docx, pptx, xls, xlsx, hwp, csv, txt, xml
Calendar events
Samsung Notes
AR Emojis
Clock
Voice memos
Home Screen settings
It does NOT create an "image". Nothing for Android does that because of security. There are more complete backup options for rooted devices, but I don't know how extensive those get.
If everything you have is using strictly Samsung stuff, then it can recreate pretty much all settings on a new device as before.
However, certain kinds of data may not be carried over even if apps are. Most apps save data in a separate location that can't be copied, so you'll have to find ways of saving that data to an external location within the app. Or in the cloud if said app gives you the option to have an account to save such information to.
Email accounts may save the name, but you will have to re-input the passwords to properly log in. Contacts and calendar events that can be saved are only those stored locally on the phone and not tied to an account. If they are part of an email account like Outlook or similar, those are not included. But re-signing into those kinds of accounts should pull them all back in.
You can't think of an Android phone like a Windows PC. They are two totally different animals from different backgrounds (Windows coming from DOS, and Android is "Unix-like" by way of a Linux branch). So, system access (or lack of) is completely different. Android having a very different way of dealing with it than Windows simply assigning "permissions" to folders.