None.
Oxygen is a theme-less page builder. Once activated, it nulls any theme in use:
But it doesn't meant that you can't have access to pre-built designs.
Oxygen has what we call Design Sets. It's pre-built designs organized as full pages or sets of elements that can be loaded from within the builder (under Library > Design Sets.)
Oxygen's design sets library is growing steadily by the Oxygen team and others: