Well, revenge can be seen as a theme too. There are characters who are seeking vengeance for past wrongs done to them or their loved ones. Also, the exploration of different forms of magic and power is a significant theme. The various characters possess different magical abilities, and how they use or are used by these powers is an important aspect of the story.
In general, the Dorohedoro anime is quite true to the manga. It captures the key elements and the unique style of the source material. Some small adjustments might be made for better visual presentation or to fit the animation format, but they don't deviate much from the manga's core.
The Dorohedoro anime ends approximately at a certain point in the manga, but it's not an exact one-to-one match. Some storylines might be slightly different or left out.
En is a very complex character. His power and his role in the world of Dorohedoro are quite fascinating. He has a certain arrogance, but also a vulnerability that you don't expect at first. Shin is also interesting. He's a bit of an enigma, always seeming to be in the middle of things and having his own motives that are not always clear. He's got a mysterious air about him that draws you in.
You might find it by searching for the specific title on the Tumangaonline website. Sometimes, it could be categorized under popular or recently updated sections.
One idea could be a crossover with 'Fullmetal Alchemist'. Dorohedoro's dark and gritty world combined with the alchemical concepts would be fascinating. For example, the characters from Dorohedoro could be exposed to the laws of equivalent exchange. Another plot could involve a crossover with 'Hunter x Hunter'. The nen abilities in 'Hunter x Hunter' could interact in strange ways with the magic in Dorohedoro's world. Maybe a character from Dorohedoro has to participate in the Hunter Exam. A third idea is a crossover with 'Tokyo Ghoul'. The idea of the ghouls' existence in Dorohedoro's setting and how they would coexist or clash with the existing creatures and characters there.