What is IX's rough plot points?
Seems to be essentially this....
A year after the events of The Last Jedi. Kylo has settled into his role as Supreme Leader of the galaxy, as Anakin pre-Darth Vader always wanted to be. Bringing order and peace. Kylo is seen as a benevolent ruler. Not a Palpatine, tyrant. Across the galaxy. But there are certain flashpoints where Kylo dolls out vicious treatment in ORDER to keep the galaxy in general order. Certain troublemakers/freedom movements have to be crushed, dealt with. Clans and pirates. Just like you see in general society. For the vast population it's all peace, jobs, homes, content lives, entertainment. But there's a percentage of the population who are criminals/etc, who live in a more dangerous realm in that same society, they have police and other criminals constantly at war with them, violence, killings going on. That's the nightly News.
Rey is probably training and growing in the Force. Poe, Finn, Rose, etc are all still wanting to take the fight to the First Order, see it as corrupt, they know Kylo personally and how bad he can or has been. Because in their minds they think they're all good and fighting evil. Hypocrites! Anyway, Leia is still out there trying to drum up support for a Resistance, which HAS grown since TLJ. She/Poe/etc are still recruiting more clans and worlds to join their cause.
Hux meanwhile has his designs on being the boss, and has always hated Kylo anyway. This time, there's no super-power Snoke. Just the still human Kylo who can be usurped, if he can get the First Order itself to side with him. Find something about Kylo to betray him with. He's feeding intel to Leia/Poe etc in the interim.
Kylo continues to explore the lore of Sith/Jedi, and wants to obviously grow more powerful. He recuits his KoR, all force users too, fellow students at Luke's academy back in the day, to come with him on a quest for knowledge/power. Pretty medieval tone abundant. Kylo early in the movie taps into Snoke's ring and sees visions of secrets out there. So there's a middle act where he's off with the KoR exploring worlds, killing clans/people getting in his way, guarding the secrets, a kind of Raiders of the Lost Ark type of thing going on. He finds all those ancient Sith/Jedi relics and holocrons, many call-backs and flashbacks to Palpatine, young Snoke, Plagueis, and prequel trilogy lore in this medieval quest sequence.
Whilst Kylo/KoR are off doing all this, the Resistance has increased their attacks on First Order bases and strongholds, due to Hux intel, and treachery, as he tries to create a situation where the First Order loses faith in Kylo as leader. Rose, Lando, Maz, Poe, Finn, etc all engaged against the FO in some big battle whilst Kylo is away on his quest.
Rey meanwhile has also started her own adventure for more power or to reach Kylo himself and appeal to him, because she also learns some startling things herself in her visions, training, and encounters with Force Ghosts and relics/artifacts. They are enemies but also the two strongest force wielders around, and naturally drawn to each other. Probably some more Force Skyping going on. Maybe even a scene where they are both together alone, intimate/sympathetic, caring touches etc, whilst all the others are going at it in battle on other worlds.
Eventually tho, they resume their hostilities due to disagreement about Sith/Jedi lore, not joining forces, etc. Rey goes back to help Finn/Poe/etc who are in grave danger. Kylo goes back to take charge of the FO and resolve the Hux situation, as he now realizes his treachery.
The movie thus concludes in the final act, with a huge space/ground war, where everyone dies. Chewy, R2, C3, Leia, Lando, Poe, Finn, Rose, even Kylo and Rey.....but it ends with a child of Rey/Kylo alive. Just in case Disney may want to backtrack in the coming years and re-continue the "skywalker saga" in movie form, or push that skywalker saga continuation off into purely books and comic editions.