I would like the images captions to be _below _the images in the masonry gallery instead of overlapping the bottom of the image. I see various options for caption style, but nowhere to determine the placement of the caption?
As you have already noticed, there isn't a built-in feature in Toolset that manipulates the captions position. You will need to add a custom CSS, in order to display it at the desired position.
For example, I have checked the page you linked above, and reached to this code that perhaps is a bit near from what you need:
Just test to add it in the Appearance -> Customize -> Additional CSS section of the theme. If needed, make some corrections according to your preferences.
Note: the possible solution provided is to be used just as an informational one. Please remember that custom coding is out of the scope of our support, so we can't create, debug or modify code for you and it's your responsibility to maintain it. We hope the one we used as an example could point you in the right direction. Please check our support policy: https://toolset.com/toolset-support-policy/
Thanks for your understanding. If you need anything else don't hesitate to contact us.