In functions.php, in the_bootstrap_widgets_init(), before_title and after_title are set up for <h2>. In sidebar.php, before_title and after_title are set up for <h3> on the archives and meta widgets.
The <h2> in functions.php is prevailing, but which should it really be?
(Just striving for consistency in the base theme. I'm probably going to override it anyway because <h2> is definitely too large and even <h3> is iffy.)