This plugin does the job alright.
Few formatting issues I have with it:
When displaying thumbnails, I'd prefer it to maybe grab the thumbnail instead of the featured image because the featured image isn't necessarily in a square so when resized it will display funny. Also, when it doesn't show the max number of related posts, it would be nice if the related posts resized to fill the full width.
Technically, it seems to work ok.
I don't really have time to research other plugins right now so it'll do for now.