There are three areas at work here:
1. location on the PC of newly downloaded podcasts
2. location on the HH for sync'd podcasts
3. general location for newly created audio files (non-podcast)
Number 1 is controlled by Directory and Filename location in the Podcast Tag and File Renaming Rules in the Podcasts feed settings. Unfortunately, this is an older interface, and the input fields do not support expressions. Only the pre-defined fields are supported (see the pull downs in the dialog).
Number 2 is generally controlled by the HH settings in Options > Handheld > File, Paths & More > Audio Path. But I believe for certain devices, such as Sanza, either the device or MC overrides and places certains types of files (such as podcasts) in internally defined locations. I don't know enough about the various devices to give better info here for your device.
Number 3 otherwise controls the placement/naming of files of a given type created by MC (e.g. ripping, Renaming, etc.). This setting does not override numbers 1 and 2 above.
The original expression you were using works in the two cases, because they are mutually exclusive (media sub type is either one or the other). But the expression was not doing what you wanted, simply because the ELSE portion of your IFs were empty, and instead placed *outside* the IF statement. To nest IF statements, ensure the TRUE or FALSE cases are entirely contained within the IF statement. Eg:
if(condition,
true case,
false case
)
where nesting would be:
if(condition1,
true case,
if(else_condition,
true case,
false case
)
)
so ultimately you want something like:
if(IsEqual([Media Sub Type],Podcast),
PODCASTS\[Album],
if(IsEqual([Media Sub Type],Audiobook),
AUDIOBOOKS\[Album Artist (auto)]\[Album],
MUSIC\[Album Artist (auto)]\[Album])\
)
)
However, you must remove the newlines I added above (for clarity) in certain expression edit areas such as the HH's file location (it uses an *older* expression editor interface that does not support newlines):
if(IsEqual([Media Sub Type],Podcast), PODCASTS\[Album], if(IsEqual([Media Sub Type],Audiobook), AUDIOBOOKS\[Album Artist (auto)]\[Album], MUSIC\[Album Artist (auto)]\[Album]))
Alternatively, I provided a working IfElse chain. Try any of these in an expression column to test.
Regarding the issue with given podcasts not having Media Sub Type set, can you give more details so that someone can duplicate the issue? This should always be set with using the podcast feed interface and MC downloads as per feed instructions. It won't be set automatically if you use MC or some other tool to download manually.
As for organizing by frequency, you can construct a view that displays the podcast downloads in any fashion you want. I have a Downloaded Audio view under Audio, that shows organized downloaded audio such as Podcasts, MC Scheduler downloads, or other things I've placed there. Would this work?