Hey,
I changed the calculation of new width and height for the watermark to override the provided one. Here is a gist with the code i used https://gist.github.com/vpsnak/eacee0aa9b3315c422f99242772bb9f7
The result is that the watermark is downscaled to max_width and max_height (now defined as 25%) of the image applied to.
Here are 2 screenshots of different ratio images with watermark applied using the above sizing
https://prnt.sc/s0wd0r
https://prnt.sc/s0wdbq
My suggestion in my previous message was that you could use apply_filters before the sizing of the watermark to provide developers the ability to add custom sizing like i did above instead of changing the plugin code and having to manually update plugin for every update afterwards.
if you need more info i will be more than happy to help.
Thanks for your time