Can you explain why disabling sets is bad? Why is the option there in the first place then?

I've scanned all my art files and everything checks out ok.
However, I am willing to give it a try but I want to be sure on how to setup properly.
So here's what I am going to start from scratch and re-run the mame extraction so that I end up with:
I:\Mame
+------artwork
+------ctrlr <-- contains not compressed files
+------docs
+------hash
+------hlsl
+------roms <-- contains compressed files, one per game
+------samples <-- contains compressed files, one per game
[files... like mame.exe, mame.ini]
I'll then create the following structure inside the artwork folder:
+------artwork
+-------artwork <-- bezels and layouts, one zip per game
+-------bkground <-- contains not compressed files
+-------cabinets <-- contains not compressed files
+-------cpanel <-- contains not compressed files
+-------flyers <-- contains not compressed files
+-------icons <-- contains not compressed files
+-------manuals <-- contains not compressed files
+-------marquees <-- contains not compressed files
+-------pcb <-- contains not compressed files
+-------snap <-- contains not compressed files
+-------titles <-- contains not compressed files
Will I need to amend the mame.ini configuration file to add all those subfolders or is Mame smart enough to figure it out?
Also, for now the files inside the subfolders are uncompressed and although I could compress them using 7z and a solid archive (with a small solid size) I am not sure of the impact it would have on Mame upon loading a game. It would certainly make an impact on the storage size though...
