Here is all of the difference between Dragon Ball RWBY'S Daima vs cannon
Like Ruby goes the demon realm alongside Shin frist BC she beat Majin Buu
Ruby makes sure their ship isn't destroyed or saves it from crashing thus they arrive to their locations faster
Vegeta, Piccolo, Penny, Bann all head to the demon realm once they're picked up
Ruby fights Tamagami 3 and wins using Kaio-ken x100, gets the Dragon Ball
Ruby shrinks down the Dragon Ball with magic and puts it in her pouch (Dragon Ball is never temporary stolen)
Knowing of Majin Buu's revival, Dr. Arinsu followed Babidi and the Supreme Demon King Dabura to Remnant in Universe 7. After Vegeta's failed self-destructing sacrifice to destroy Majin Buu, Dr. Arinsu claimed a fragment of Majin Buu before he could reform and took some locks of Ruby's hair after noticing she was unconscious after Vegeta had knocked her out to fight Majin Buu alone. Sometime later, Dr. Arinsu gave the fragment and Ruby's hair to Marba, Majin Buu's true creator, to create another Majin for her to help her become the new Supreme Demon King. Marba would then begin the process of creating a new Majin
Majin Kuu and Majin Duu are Majin's created by Marba using a Saibaman seed alongside some of Ruby Rose's hair infused with the essence of Majin Buu and other factors. This not only caused them to have silver eyes, thus Preservation Energy but also make them stronger then cannon. She only took Ruby's DNA because of her Preservation Energy, something she could actually somewhat sense from Ruby and given how calm Preservation Energy is in her mind it'd make controlling a Majin much easier and she was right
Majin Kuu fights Tamagami number 1, and was evenly matched with him but gave up after a while seeing that as the much smarter opinion after seeing the Tamagami power up even further
Shin explains his kind come from five Glind Trees but they have since died out. When Penny points out that it means that his race will one day become extinct, Shin confirms it. Both Ruby and Penny look at one another thinks to use their magic to restore the five Glind Trees using Afteran Magic
Vegeta claims that he will be the one fighting Tamagami Number Two, much to Bann's frustration. However Penny says she'll fight Tamagami Number Two, upsetting Vegeta but he agrees much to his displeasure when Penny threatens to not fix the gravity room she built for him
Penny fights Tamagami Number Two using her Winter Maiden Powers and kept up a good fight until Neva provides his creation with some additional power. With the Tamagami's power having grown significantly, forcing Penny to go Ultimate, she beats Tamagami Number Two and passes the trick question test
Ruby reveals that Penny unlocked her potential after the events of the Buu Saga and Weiss, Blake, Yang, Nora, Ren, Jaune also had their potential unlocked. Ruby convinced Elder Kai to do this not just because she saved the universe against Majin Buu but also threatening to turn him into a cloud of molecules again with her Semblance
Majin Duu is made, again with Ruby's DNA making him stronger then cannon
On planet Mega, Penny and Panzy finish repairs on the plane while Ruby choses to solve the problem of the Megath child and their dog by growing to the size of an adult Megath with magic after going Ultimate to tell the kid off to buy time for the ship to get fixed and it actually worked
Upon arriving at the Sir Warp they find that it is not operational. Neva realises that Gomah must have issued the order for the Sir Warp to be shut down due to seeing them heading to the first Demon world so fast, so with no other choice Ruby and Penny uses their Magic to remove the barrier surrounding the Demon Realm Tunnel, Impressed by their abilities, Neva tells Penny and Ruby (Who whenever they use Ultimate use their magic to make themselves Adults again) that their magic seems to ignore universal laws and let's them do whatever they think they can do, a very powerful and versatile ability and he is glad that they're using the power with pure intent as manipulating reality like that is a selfish power and selfish actions lead to doom. Neva then says he was the one who conjured up the barrier originally and explains why
Third Demon realm differences:
Ruby and Penny stop holding back and go Ultimate and turn into adults again via their Afteran Magic and power Nullify all the attacks the Gendamerie soldiers use on them so they can't he paralyzed at all and solo them all before the Kadan Force arrived to help
Bann, Ruby, Penny, Vegeta, Piccolo and Shin head inside the palace while the others wait outside and like normal Panzy has a curious feeling and later enters the castle as well
Bann and Vegeta play play rock, paper, scissors to decide it as both Bann and Vegeta haven't fought yet and Bann wins and fights Majin Kuu and makes Bann go Super Saiyan 2 against him but the fight is interrupted like normal
Vegeta attacks Evil Third Eye Gomah like normal. Bann suggests they all attack together as he is joined by Piccolo, Ruby, Penny, Shin and Glorio. Even working together, the group find no leeway
Ruby doesn't drops the pouch containing the Medi Bugs during all the commotion unlike Goku as the Medi Bugs are in her pouch on her belt
Majin Kuu, Duu join in without anyone telling them to do so to help and Tamagami number 1 joins in to help too via Neva telling him to like normal
Ruby chooses to use Kaio-ken x 100 and Penny choses to use her Winter Maiden powers after they noticed Gomah adapts to their power
Neva unlocks ssj4 for Bann as Bann himself explained at the end of the arc "Hiding? You mean super saiyan 4? Nah, I had a general idea to mix Great Ape with Super Saiyan, but didn't know how to, guess all I needed was a little push hehe" (The little push being Neva's Magic unlocking his potential), however it looks like GT's ssj4 just with enlarged forearms
After some time passes, the other fighters join in (Unlike normal Vegeta joins in after getting healed by Penny's Afteran Magic), having got a second wind, join back in on the fight and Vegeta goes Super Saiyan 3 to help fight
Gomah becomes stronger then ssj4 Kid Goku like normal via the Evil Third Eye's RPL and like normal Glorio wished for everyone to be returned back to their normal ages
Vegeta fights Gomah like normal alone, and after Bann suggests to fight instead Vegeta, refuses and continues to battle alone but Ruby steps forward and tells Vegeta to let someone else take over or she will never spar with him again. Vegeta immediately pulls out of the fight because of Ruby's threat
Ssj4 Adult Bann vs Gomah goes the same as normal, Gomah regenerates and is too powerful so Penny and Ruby go Ultimate to join ssj4 Bann against Gomah, fighting on par with SSJ4 Bann however even this isn't enough as Gomah adapts to their power again forcing Ruby to use the fusion bugs with Penny to fuse into Rubenny and in base one shot a hole through Gomah's stomach pushing him up into the hole in the first Demon realm caused by Bann's Kamehameha and then Rubenny goes Ultimate, charing up a Rose Kamehameha Cannon while Gomah is regenerating and fires it at Gomah and using her Afteran Magic's Subjective Reality to nullify any Reactive Power Level or Reactive Evolution BS to completely vaporize him and kill him
After he's dead by Rubenny, she defenses willingly by using their Afteran Magic to defuse themselves
After the fights over there's a debate on whether or not Ruby or Penny should become the new Demon Queen because their fusion killed Gomah, but they want to leave back to Remnant so Ruby brings up a good point, it's because of Majin Duu and Arinsu who are residents of the Demon realm who did help fight Gomah and help them win so Ruby suggests Majin Duu become the new Demon King, Ruby and Penny even makes sure to fight Majin Duu and pretend to lose to him to make it official too (lol) and so Majin Duu becomes the Supreme Demon King with Dr. Arinsu as his Vice Supreme Demon King and Glorio, Neva, Marba, Kadan, and Majin Duu as his Ministers.
Meanwhile Degesu is sealed away for 99 years
Ruby and Penny visit the second demon realm before heading to the third one to restore all the Glind Trees using Afteran Magic and then visit that shop with the medi bugs and find out Evil Third Eye but two more are revealed to exist in a shop in the third Demon Realm
Vegeta basically asks Penny or Ruby to use their Afteran Magic to give him ssj4 so he can be on a equal playing field with Bann and them so sparing against them they won't need to hold back. So they do it and Vegeta gains ssj4