
The begin part of the novel is soo different. They skipped a whole arc and some arc are in different order, and my guess is the ML was not introduced yet in those arcs. The manhwa is more focused on the couple unlike the novel. For me the novel feels more like a harem with the Duke as the Main ML and that is not bad cause they tell you more detail about the retainers and their relationship/friendship with their lord. I like both versions a lot.
The manhwa is better in showing Duke s emotional side and ofcourse its r18.
The novel has better world building and tell you more about the game mechanics, can be too deep in detail in some parts.

I cant say as sub characters but more one sided love interest side characters.
They are more fleshed out as characters. Mc treated them as people not NPC characters. He went on walk, ate with them and stand by their side if they lvl up.
They all know that ML is his main interest but still got the guts to send MC gifts behind ML back every day hahaha. ML is also "sometimes" understanding and let his retainers sleep in their room together to bond during hard times.
They don't have a large role to show in every chapter but they do have their own moments and the bond to show off.
I started reading the novel for this and I've got to say the manhwa is so good! Dare I say maybe better than the novel kinda? In the sense that having illustrations really adds to the story the vibe and the feelings idk it doesn't happen often so I was just glad to see it
I'm also extremely relieved to see my baby healed again that whole arc was traumatizing tbh