While it still isn't super clear to me, I was able to get the behavior I wanted by adding the following change to class-album.php:
'function getSubalbumSortKey($sorttype=null) {
if (is_null($sorttype)) { $sorttype = $this->getSubalbumSortType(); }
if (is_null($sorttype)) { $sorttype = "Filename"; } // added this line
switch ($sorttype) {
case "Title":
...'
This made it such that newly created albums that contain subalbums will sort the subalbums using the Filename by default. It seemed to default to the manual sorting order before this change, which is the setting that i was thinking I would have been able to set from the "General Gallery Configuration" section under the "Options" tab.
I hope that makes sense. Basically I couldn't figure out how to set a default / global setting for how to sort subalbums (at all levels). It seems this might be nice to have in the admin section.
I'm migrating from Gallery where you basically set your global preferences, then can override any setting on a per albums basis. It seems ZP is similar to that, but is a bit different at least when determining how to sort subalbums in new albums. BTW ZP is a breath of fresh air after maintaining a large Gallery site.
Let me know if I'm off my rocker, and regardless, thanks for chiming in.
Cheers, Rich