Can it really be called "MISCHARACTERIZED" ?? These are all just modifications they made i think, that makes the drama even more appealing !!

Liuyi being softer or more openly affectionate doesn't necessarily mean he's "out of character", it can be the drama's way of externalizing emotions that are much easier to convey through internal monologue in a novel. It's actually good if they made Liuyi a little softer.

As for the "flower scene", the "safe place" convo, or "Liuyi staying at Chusan's house", these changes seem designed to build emotional intimacy on screen. A TV audience can't read a character's thoughts, so adaptations often use actions and dialogue to communicate feelings that were internal in the source material. (And the flower scene is literally my most favourite scene from the drama. So I thank them that they actually made it.)

The same goes for Chusan. Just because in the novel he is more proactive and straightforward after realizing his feelings doesn't mean the drama can't explore his vulnerability differently.

And i don't think Chusan is afraid at all lol. As you said, he's the "best actor", two faced, right ? So he might be just acting to not get in trouble for involving with gangsters at first. But later as he got involved with Liuyi, he said to his face multiple times that he would never become his lackey without any fear.