Well, a common feature of a typical romance manhwa is the focus on the emotional journey of the couple. There's usually lots of cute moments, maybe some obstacles they have to overcome together to strengthen their bond. Also, the art style tends to be very appealing, making the characters look charming and the settings dreamy.
I think the ideal protagonist for a manhwa romance could be someone who is brave in facing challenges and shows unwavering loyalty in love. They should have a unique background or story that adds depth to their character and makes the romance more compelling.