mixing tf geometry_msgs StampedTransform PoseStamped

edit

Iam looking for the best practice to get from camera_frame->marker_pose to a map->odom transform to be published as amcl replacement. There should be an easy way, but it turned out to be a ugly mixup of datatypes and conversions that work for one but not the other etc. lots of legacy discussion out there. Iam not even sure why there are seemingly identical tf and geometry_msgs types out there, whats state of the art? Thanks.