The srcset attribute only exists in the context of the HTML img element. It's a way of declaring to the browser the relevant available image dimensions when displaying the image with an img tag.
If you are outputting the URL of an image, WordPress generates several files for different sizes of the same image, and you can output the URL of any one of those sizes.
If you were manually constructing your own img tag rather than using the one generated by the Types shortcode and you wanted to include a srcset attribute, you would have to manually construct it by using the Types shortcode multiple times to generate each of the URLs.
How do i use toolset to manually construct my own img tag?
If you were manually constructing your own img tag rather than using the one generated by the Types shortcode and you wanted to include a srcset attribute, you would have to manually construct it by using the Types shortcode multiple times to generate each of the URLs
So you would be looking to reproduce something similar, generating the URL parts of the above using multiple insertions of the types shortcode with the url='true' parameter, which would go something like...
