Actual product size is very small, please advise how we can increase the thumbnail for desktop and mobile view.

Better if we can control the height and width separately, to try what looks good.

https://carnity.com/store/category/8-off-road-driving-course

This one might help... There are others

 

Please suggest other ways too, as I'm super scared of above plugin author.

I dont mind editing codes, little bit here and there or pay for any other similar plugin/app.