There is indeed no way to have Sho post flow in the flex columns.
The way your reference site is doing it is simply by setting a minimum height for each post that is longer that the longest post.
To do that on your page, add the CSS rule below to the theme Global Custom CSS rule box (adjust the height value to what you need)
.home .post-area {min-height:400px;}
It will help your maintenance of the site if you try to have fixed excerpt length and image size.
For the post title, Check all the options that are available for the position of the featured image in Customize (in WHERE mode) > Post Specifics > Featured Image > Featured Image Excerpt posts > Position of the Featured image.
To get the post title above the featured image just use “with Content Top”