I already answered this question here: How to change default template files in Android Studio .
Basically, you need to look at the file recipe_fragment.xml.ftlso that you know which files are used for the template.
The default template files are located in the folder
...\Android\Android Studio\plugins\android\lib\templates\activities
, BlankActivity, , ../common/recipe_simple.xml.ftl ( ) , , BlankActivity
...\Android\Android Studio\plugins\android\lib\templates\activities\common\root\res\layout\simple.xml.ftl
RelativeLayout LinearLayout ( ), , , , .