He might have a tall and imposing stature, with piercing eyes that still hold a hint of his otherworldly power. His hair could be a dark color, perhaps black or a deep shade of purple, and it would be neatly styled.
His human form could have a chiseled jawline and a face that is both handsome and a bit angular. His hands might be long and slender, with a certain grace to them, yet still look strong enough to wield great power if needed. His overall appearance would be a blend of human attractiveness and a touch of the otherworldly.
One possible plotline could be Momonga exploring the human world in his new form. He might encounter various human emotions like love, friendship, and jealousy for the first time. Maybe he gets a job to blend in and has to deal with a difficult boss or annoying coworkers.
She would likely have long, flowing hair, perhaps a golden color like the sun, to represent her divine origin. Her eyes could be a bright, piercing blue or amber, full of an otherworldly intelligence. She would have a graceful figure, with a certain poise in her stance that makes her seem both approachable and yet somewhat ethereal.
His strength could show up as superhuman physical abilities. He might be able to lift extremely heavy objects with ease.
One common theme is his adjustment to the human world. Since he's from a different form originally, how he copes with human emotions, relationships, and society is often explored.
In his human form, Acnologia might be more complex. As a dragon, he's mainly seen as a destructive force. But as a human, he could have emotions like regret, love, or compassion. For example, he might feel remorse for the destruction he caused as a dragon.
With Sakura, she might be initially scared but then come to see Naruto as someone she needs to protect even more. She could develop new medical techniques specifically to help Naruto in case the Kyuubi's power ever goes out of control. And she would probably be more in awe of his strength and try to learn from him how to be stronger herself.
Give the Okami in human form a backstory that ties them to their original form. Maybe they were cursed to be in human form as a punishment or they chose to take human form to better understand humans. Their actions should also be influenced by their Okami nature. For instance, they might be more in tune with the phases of the moon and act differently depending on whether it's a full moon or a new moon. Their speech could also be a bit more formal or archaic, reflecting their otherworldly origin.
He might become more empathetic in his human form. Since humans have a wide range of emotions and experiences, Kurama could pick up on these and become more in tune with the feelings of others compared to when he was just a fox demon.
You can try fanfiction websites like Archive of Our Own (AO3) or FanFiction.net. Just search for 'Momonga human form' on their search bars, and you'll likely find a variety of fanfictions related to it.