For some reason nearly all movies of this kind starts out with a misogynistic man offending women with his clueless and sexist behavior.
In this movie, as in many others, a witch decides to teach him a lesson. The witch in this movie is of a younger and more sexy model, that is true, but the basic storyline is the same.
Since this is a porn movie, the acting is pretty bad. There is one exception, though: Whitney Wright does a good job playing the role of post-transformation, post-traumatic, Ryan.
There are no bathroom scenes of the "oh God, where did my cock go" type. It actually takes some time before he realizes what has happened, and that is when his ex-girlfriend Alexa turns up at his door. This obviously ends up with him cheating on his male self as Alexa's lesbian lover.
Porn movies including gender changes most often stay away from the male to female transformer having sex with a man.
I guess this might cause some serious identity conflicts in the regular straight male audience watching the film. This was what happened in Wicked's previous gender bender movie, Switch, where a man swapped bodies with his wife (played political porn celebrity Stormy Daniels.
Cursed, however, ends with a bizarre scene where the female Ryan meets the male Ryan and have sex together in the hope of merging their two bodies into one male one. This never makes any sense, and even less so when we find out that the witch intended to switch him back, anyway.
In other words: The gender change is mainly a silly plot device that does not really do it for people who are looking for transgender erotica.