Solution for this topic

I wish to use overlay 3 in my gallery with the minimalistic style. I wish to hide the descriptive text but it doesn’t seem to be in any tags (image attached). Please could you advise how?

You can achieve it by adding the following CSS code in the Custom CSS code option of your theme on the below path.

Admin Area -> Appearance -> Theme Settings -> Custom Code -> CSS Code

.sh-portfolio-overlay3-data {
    font-size: 0 !important;
}

Could you please also advise how I can change the hover state of related items to match that of the portfolio.

To achieve this you have to develop custom CSS code like developed on the following page.

http://codepen.io/oloman/pen/nIsib

The mini images are in relation to there being a gallery set on the page. I wish the main image to appear like the gallery on the gallery slider page but using this layout.

You have to develop custom code to achieve this.

Developing custom code for custom functionality is beyond the scope of support that we provide here.

If you are not a developer then you can consider hiring a developer to develop it for you. You can hire a developer from any freelance site. Shufflehound recommends the developer https://www.upwork.com/freelancers/~011652ffec8865c6d5