If the Default Child Template attribute of the parent item is Text, Insert will insert a new Text child, and Shift+Enter will insert a Text sibling.
As far as inserting via the Alt+Ins or Shift+Alt+Ins menus (pressing Alt+Shift with left hand and Insert with right isn't too bad), with two templates starting with T, you do have to press T twice and then Enter. But you can rename one of these templates to start with a different letter and then be able to type just the first letter once to select that menu item.
The Alt+Ins/Alt+Shift+Ins shortcuts are not customizable in UR, but you could use a
macro tool to define your own keyboard shortcuts to select menu items, etc.