As of Bricks 1.9.4, there is no option to set a breakpoint at which the sticky header should stop being sticky.
We can add the following block of CSS code in the header template → Settings → Page Settings → Custom Code → Custom CSS:
@media (max-width: 991px) {
#brx-header.sticky.on-scroll {
position: static;
}
}
Replace 991 with your desired breakpoint.
Reminder: This is how sticky header can be enabled in Bricks when editing the header template ↓

For more/better control of the site header, you might want to use Header Extras / Rows from our BricksExtras.