Well, as far as I know, the continuation of the Darling in the Franxx manga is a bit unclear. It could potentially continue depending on various factors like the popularity and the creator's plans.
Overall, the Darling in the Franxx manga is relatively consistent with the anime. Some characters' expressions and minor plot points might vary, but the core story remains the same. It's more like two sides of the same coin.
The anime of My Dress-Up Darling typically ends at a certain point in the manga, but it's not always an exact match. Sometimes, adaptations make slight changes.
In general, the anime of Dressup Darling follows the manga closely. There might be some tweaks in the animation style and a few added details for visual appeal, but the core story remains the same.
I'd recommend starting from the chapter where the anime ended. That way, you can seamlessly continue the story and discover new plot developments. But if you want a full experience, starting from the first chapter isn't a bad idea either.
Since we lack the details of the 'Mona Darling full story', it's difficult to define who Mona Darling is precisely. She might be a protagonist in a love story, facing challenges in her relationship. Or she could be a strong - willed character in a thriller, fighting against some sort of danger. There are countless possibilities depending on the nature of the story.