SMPC caches nothing but metadata (artist,albumimages and one text about album/artist).

During application execution phase SMPC recatches the filelist for every path when you open the files page. For example. if you open / in filebrowser it catches the data fresh from mpd. if you go back to the SMPC Homescreen it releases all data to not put pressure on the device memory. This is the case for all MPD datarelated pages. As soon as the page gets pushed away, SMPC frees the data. This allows a small memoryfootprint.

For MPD itself there is no differention of filelist and database. If you want to browse you files in MPD and ANY client you need an mpd database.