Most of the application residues will remain in /data partition specifically, /data/data/com.packagename where package name represents the particular application package.

In these directories that's where you usually find app's databases, configs as well as preferences files, which are normally preserved during reinstalling or updating etc (which is the reason I suspect they're preserved even during uninstalls)

In any case, you can actually scan these residual or "corpse" files with 3rd party applications such as sd maid to have a clear breakdown.

NB: this /data partition is not visible to non root users, and you will need elevated privileges to view and perform file operations from that partition.

Some applications may leave the application residues in /data partition specifically, /data/data/com.packagename where package name represents the particular application package.

In these directories that's where you usually find app's databases, configs as well as preferences files, which are normally preserved during reinstalling or updating etc (which is the reason I suspect they might be preserved even during uninstalls)

In any case, you can actually scan these residual or "corpse" files with 3rd party applications such as sd maid to have a clear breakdown.

I tested on Android 4.3 perhaps things have changed since then, but at in basing my answer on that