I can make a plane this way.
import unreal as ue
ell = ue.EditorLevelLibrary
eal = ue.EditorAssetLibrary
mesh_actor = ell.spawn_actor_from_class(ue.StaticMeshActor.static_class(), ue.Vector(0, 0, 0), ue.Rotator(0, 0, 0))
mesh_comp = mesh_actor.get_component_by_class(ue.StaticMeshComponent.static_class())
temp_mesh = eal.load_asset("StaticMesh'/Engine/BasicShapes/Plane.Plane'")
mesh_comp.set_static_mesh(temp_mesh)
mesh_comp.set_editor_property("relative_scale3d", unreal.Vector(thickness, 1.6, 0.9)) # Set the aspect ratio of image