I use Inkscape. You really can’t create a template per say as I understand it. If I’m mistaken please let me know. Since most cake toppers are text based you have to do multiple operations to get to a cut able shape Svg based. Best bet is to watch some you tube tutorials on specific actions needed for that project.
For cake topper you need basic text manipulation, object to path, creating shapes like square or oval or with bezier tool, and finally how to punch out, join, exclude parts of paths to get final shape desired. If not familiar with software it’s going to take a while to figure it out but once you know the steps it’s like second nature auto pilot fast.