It's nice to hear from you! I wish you a happy new year too 🙂
Category archives – My apologies, but I don't recall the exact conversation. I'm guessing by category archive pages you mean the ones when you click on a category (for example under a post), then it takes you to a page listing all the posts belonging to that category.
In this case it's basically searching for categories and returning them as results, which you can define on the General Options -> Sources 2 panel.
Category custom Fields – Yes, exactly that. Taxonomy term metadata is a relatively new feature in wordpress (since 4.4) so it's not yet implemented in Ajax Search Pro, but it's a work in progress.
I'm going to add an extra field to the General Options -> Sources 2 panel to select term metadata – so it will be possible to search for Categories/Terms based on their metadata.
However I'm not sure if I'm going to take it a step further to “search posts based on their categories metadata” – as this sounds arbitrary to me, since category meta is not directly an addition to posts, but the actual category (or term). Although I'm not sure about this yet.
If you like my products, don't forget to rate them on codecanyon :)