Hello James,
For large models visualization it is better to generate the tiled model in Metashape and transfer it to Viewer via TLS format.
Regular textured mesh models can be exported to most common formats, like FBX, OBJ, for example. But usually such formats do not support georeferencing, so I recommend to consider using tiled models for your needs. If you have already generated a mesh model in Metashape, then you can use it as a source for the tiled model generation to save some processing time and then just export.
Not sure, what kind of issues you are experiencing following the tiled model approach.