hi ahamed,
‘golden ratio’ or whatever you call that relations is nothing that can be automated in a perfect way (nearly no way from the theme itself!) – its something you have to find out considering many values. especially when it come to website-design!
so the tool you linked to is a good point to start and as tom suggested easy to transfer the values into GP. but up from that point the work is only beginning :-).
cover the rules of ‘golden ratio’ throughout a complete website over all responsive possibilities is kind of ‘mission impossible’ and much more than collecting three or four values for font-sizes.
‘incorporated into theme’ is kind of funny, because when you know the rules of readability, usability and even ‘golden ratio’ you can use nearly any kind of theme and set up what you want to…
in that terms GP surely provides you with the best possibilities you might think of!!
the rest is up to you ๐
edit: forgot something… for best results regarding responsiveness in this case you might consider using ‘elementor’ page builder – this one provides you with great tools for responsive scenarios too. together wit GP a great team! cheers.