Those customizations are possible, I'd recommend purchasing a pro support and asking the pro-support team for customizations: https://wpforo.com/pro-support/#plugin-support

Yesterday, I tried the wpForo plugin for the very 1st time and I must say that I'm honestly impressed by my first impression of this really great forum plugin. So thank you very much for creating this :-)

Now I consider buying at least two of the available plugins ("Advanced Attachments" and "Topic Custom Fields"), but I'm not quite sure if they will allow me to do what I really need the most... and that is to allow me to create a layout like this, that will show the 1st attached image on a "topics list page" like this?

Next, I am a bit concerned about how much webspace that will be required if I start allowing my users to upload lots of pictures with large file sizes to my webpage... so I wonder if the "Advanced Attachments" plugin has a built in feature to resize and transform the attached images to modern image formats like "WebP" or "AVIF" during posting to my site... or will it work together with WP plugins like f.ex. "Modern Image Formats"?

Last, I wonder if the "Topic Custom Fields" plugin will allow me to list some of those custom fields also on the "topics list page"? By "topic list page" I mean this page:

In other words, I want this...

...to display the same content as this:

Will this kind of customization be possible with any of the plugins you have to offer?