Did Chu Wanning enjoy the rape and actually consent to everything with Taxian-jun?
[2HA spoilers for the whole book]
Long story short -- it's complicated.
But for the more expanded answer (in my opinion).
He ALWAYS loves the act of having sex with Mo Ran. He loves Mo Ran's body, is completely and fully attracted to him (and is attracted to no one else BUT him), to the point where his sexual desire for Mo Ran is capable of overpowering all his ascetism he has built up his entire life. All Chu Wanning's reservations and shyness melt in the face of Mo Ran, and all that's left are residues in his failing attempt to save face. He loves Mo Ran, he loves Mo Ran's dick, he loves getting dicked down, he loves getting ravaged, he loves when Mo Ran is rough and does whatever he wants, and he finds it very hot.
He loves Mo Ran's overwhelming love and desire for him. He loves being loved by Mo Ran. But most of all, he loves to make Mo Ran happy and wants Mo Ran to feel loved too.
What he didn't love regarding the rape was the context and reasoning around it.
Pre-flower knowledge: he loathed that Mo Ran fell into madness seemingly of his own accord, hated that he subjugated the entire world and kidnapped and raped him and committed unspeakable deeds. He hated that the boy who used to be so full of love and life and wanted to be a good person became this monster who fell into darkness and was seemingly reveling in it so he could get his revenge after Shi Mei's death. He thought Mo Ran was "deficient by nature, beyond remedy" and wanted to kill him. And he hated himself for being a bad shizun and failing to prevent Mo Ran from going down this path.
Post-flower knowledge: he blamed himself entirely ("it was I who wronged you, I won't blame you in life or death") and he started to engage in all the sex willingly (even if he hated it and it was extremely hard for him to go through) because he knew it wasn't Mo Ran's fault (and he had to go along with it in order to hide his newfound knowledge). He thought it was his fault for not detecting the flower in Mo Ran sooner, he thought it was his fault for thinking Mo Ran committed all his crimes of his own accord, and he thought it was his fault for failing to protect Mo Ran. He knew that Mo Ran was incapable of feeling genuine happiness and love at that point, and all that was left of Mo Ran was a vessel of hatred and obsession and lust. He wanted to love Taxian-jun but couldn't show it (at risk of being exposed to the mastermind behind the flower). All that was left that he could do was go along with Taxian-jun's whims and covertly hatch up a plan to save him (which did end up being successful because Chu Wanning is a badass).
What he hated about the rape pre-flower knowledge was that Mo Ran had fallen into darkness, he was no longer the boy from before, and he was truly evil. What he hated about the rape post-flower knowledge was that Mo Ran was suffering and getting tortured, and Chu Wanning had to witness it firsthand while also getting tortured whilst blaming himself for not protecting Mo Ran.
And what he REALLY hated about the rape was NOT the sex itself → it was Taxian-jun's disrespect and complete disregard for Chu Wanning as a human being. As a person who has agency and feelings. As someone who deserves to be loved properly. Taxian-jun wanted to use Chu Wanning just for his body, as an object of lust who doesn't deserve to be loved, as an object of loathing as revenge for letting Shi Mei. He forced Chu Wanning to become his concubine Chu Fei against his well, and then forced him into having sex.
This is especially hard because --as revealed through Chu Wanning's backstory-- Chu Wanning was created by Huaizui from the Flame Emperor's divine wood. He was not born like a regular human being, and he was not treated like a human being his entire life. Huaizui treated him like a wooden replacement for Chu Lan and he would be given to Chu Xun so Huazui could apologize for what happened in Lin'an. He raised him to be the perfect replacement for someone else and he had already decided Chu Wanning's fate for him. He never treated Chu Wanning like a human being who could choose what he wanted to do with his life.
The cultivation world is no different. They all treat Chu Wanning like an untouchable god who is incapable of being on the same level as mere mortals. That Chu Wanning has no need for petty 'mortal' things like the company of others, being loved, having romance, or being sad after you get hurt or injured. He's untouchable and invincible in their eyes -- which means he doesn't get to be mortal, and he is given absolutely no grace to be imperfect or to make no mistakes. He is simply a giant tree, a looming, all-powerful, inhumane thing that watches over everyone and can take care of itself, while everyone else gets to enjoy being human. Over the years Chu Wanning has quietly grown to accept this, but it's very clear on the inside he is very hurt by this.
It hurts when everyone treats you this way, but it hurts most of all when the person you love treats you this way.
When Chu Wanning had sex with Taxian-jun, he loved the actual sex and thought it was hot. But most of all, he wanted to feel like Mo Ran loved him too. But he thought it was not true and that it could never be true, with or without the flower. Which is why the rape was so painful for him.
He hated that the sex was not an act of love.
In the 2nd timeline, once it's revealed that it's mutual and they both love each other: Chu Wanning loves ALL the sex he has with Mo Ran. It doesn't matter if it's rough, it doesn't matter if it's gentle, it doesn't matter if he's having sex with Mo-zongshi, it doesn't matter if he's having sex with Taxian-jun, it doesn't matter if he's tied up or if aphrodisiacs are used on him, he loves all of it because he loves having sex with Mo Ran, loves Mo Ran's body and dick, and he just straight up loves Mo Ran and wants to belong to him completely - whether it's Taxian-jun or Mo-zongshi. It doesn't matter if Mo Ran is insanely lustful and obsessive (also because Chu Wanning is too he just shows it in a far more subdued way EXCEPT when he gets jealous). He loves being loved and cherished by Mo Ran and treated like a spouse, instead of treated like an object. But most of all, he knows that Mo Ran is in his right mind, he's enjoying it too, and it makes him happy. He loves to make Mo Ran feel loved. And now, sex for them is fully an act of love.
(the only thing that he actually doesn't really like is voicing out his consent out loud, because Chu Wanning is a shy cat. And also let's be real, he likes it rough more then he likes it gentle but that's just down to Wanning's preference LMAO).
TLDR; Did Chu Wanning like getting raped? my answer is pretty much: it's complicated. He loves Mo Ran. He loves Mo Ran beyond anything and more than everything.