Due to the complete absence of information regarding LGBTQ+ characters or themes in the provided movie details and web search results, a comprehensive assessment of the film's portrayal is not possible. Therefore, the net impact on LGBTQ+ representation cannot be determined.

There is not enough information available to assess the film's portrayal of transsexual characters or themes. Without any plot details or character arcs, it is impossible to determine if such depictions exist or to evaluate their impact.

The movie does not contain any action or adventure elements.

The provided details for 'Mariana, 1968' do not include any information about source material or prior character establishments. Therefore, it is impossible to determine if any character's gender was swapped from a pre-existing canon.

The provided information does not include any source material, prior adaptations, or historical context for the characters in 'Mariana, 1968.' Without established canonical or historical racial identities for the characters, it is impossible to determine if a race swap occurred.