When substate regional estimates are produced, are the regions the same each time?

No. Regions are defined for NSDUH by state governments and differ between years. Definitions of the regions for each set (both maps and descriptions) can be found in the following reports:

2016-2018 NSDUH Substate Region Definitions

2014-2016 NSDUH Substate Region Definitions

2012-2014 NSDUH Substate Region Definitions