Just gonna use this entry to review all three packs contained within, both to save on space/time and because Backloggd still doesn't have the 6th DLC listed.

The Battle of Onigashima Pack is... Honestly? Probably the worst one.

Despite what the marketing said, and what OP knowledge might have you believe, the star of the show is my beautiful he/her transmasc husband Yamato. He's an incredibly strong Power type with high-damaging, high-range specials and an extra damage multiplier in FFB mode on top of the existing one.
Where he really shines is with his unique transformation, which turns him into a gorgeous wolf man with digitigrade legs- er, and also makes him a lightning-fast Speed type with crazy range and damage compared to other Speed types. The transformed specials stand out; despite being relatively boring to look at they hit like trucks and recharge scary fast. Overall, best character of the pack.

Onigashima Luffy is somewhat of a disappointment. His base form is a reskin of the post-timeskip Luffy that comes with the basgame - but with a coat. He can transform into Gear 5 which is... It's a fun transform, very strong, has some of Omega Force's most gorgeous animations, but as a transform it's very rigid and can't be customized. You can prolong it indefinitely by maintaining a combo, but as a Sky type it functionally only has one combo set which makes it a bore.

Hybrid Kaido is an odd character. The basegame Kaido was very obviously made years before Wano hit its peak and this DLC version is essentially a rebuild. He now has many of his late Wano moves which is great, but he's rather unwieldy as a Speed-type Giant, not to mention his air combos force him into his Dragon state and are equally unwieldy. Really, the real gripe I have with him is that he's just all around worse than the Kaido you can play as without buying DLC.

Anyway, onto the Film Red Pack which hilariously used to be the worst.

The reasoning for this is that Uta, the pack's flagship character, sucked. Like, god she sucked. She had worse damage than the other shitters like Chopper, Bege or Bartolomeo along with an underwhelming transformation, awful range and wimpy specials.
Mercifully we live in a world of patches and she was fixed when the next DLC came out.
Uta, nowadays, is one of the better Technique types - on par with Kin'emon and only second to Rayleigh. Her damage is exceptional for her typing and the various changes they've made to her effects, spawnable traps and specials mean she's now got enough power behind her to actually carry her through the harder stuff released in the other DLC pass.

As for Film Red Shanks, you can honestly just consult the Hybrid Kaido section because the same complaints apply. It seems as though he's made for people who can't get a handle on the original Shanks' gimmick (wherein finishing a light string with him empowers his next finisher), seeing as going FFB gives him haki empowerment for its duration. He also has that infuriating issue so many Speed types have wherein his attacks can overshoot his position, meaning followups will miss if you're attacking an armored enemy.

Fortunately the pack is worth it for one character: Koby. I was excited for him more than the other two because he's one of my favourite characters in the source material, but that excitement turned to apprehension when I found out he was a summon character like Bege or Cracker.
Good news, though, is that he's fantastic. I always wanted the Six Powers to get another rep besides Lucci and he delivers. He's fast, impactful and very fun to play - plus his summons don't feel intrusive. FFB just makes them even better, and his Film Red outfit has a button dedicated to a dramatic Yakuza-esque coat toss. Hey, he even comes with his non-movie outfit! Surprising.
Nothing fancy to say here, he's just *good.

Now onto the last pack, where much of the Sauce was saved: The Legend Dawn Pack is... Cheats! Hurray!

Gol D. Roger is as you'd expect from a character with so much in-story mythos as him. Kinda reminds me of my Xenoverse 2 modding days, where so many custom characters had obscene guard breaks and stamina drain on their normals. Though he's not a Giant type, he still shreds the armor gauge like crazy and possesses ludicrous range. His charge attacks can be... well, charged [Isn't it annoying that they're called that despite most characters not being able to charge them up?] but FFB removes the need to do this.
When I say "Legend Dawn is cheats", I mostly mean Roger. He's easily the second best character in the game, behind Whitebeard. Also his taunt lets you put his hat on which is ADORABLE.

Rayleigh is my personal favourite of the three, though. Once again he's one of my favs from the manga, for despite being a lesbian I am NOT immune to a fruity old man.
You know that thing annoying Shonen powerscalers do where they look at an old/injured/retired character and go "Yooooo imagine him in his prime though"? Yeah well Rayleigh in this game is that to a T.
He's a Technique type yes, but in function he plays like a Power type. His entire shtick as an old man is his obscenely powerful and refined use of haki, and his younger self in this game shows it off by doing what I can only describe as some Vergil-tier shit.
It's really telling that, while other characters with Conqueror's Haki have access to a special known only as "Conqueror's Haki", Rayleigh's is so fucking powerful that his special has its own name.

Garp, meanwhile, is something of a disappointment. He's a weird hybrid of his PW3 grappler moveset and a newer brawler moveset with some annoying mechanics. Namely, grapples bounce off of armored characters, and he has a sword buff mechanic like Shanks/FR Shanks/Oden/Mihawk/Smoothie but unlike those characters, it's given based on hit count - which is a problem for a character with low range and relatively few multi-hist.
Honestly, his real issue is that Power as a type is super crowded in terms of good characters, and compared to them he's far down the ladder. Don't get me wrong, he still clears half the roster, but when that half has characters like Tashigi/Bege/Chopper/Sanji/Bartolomeo in it, it's not much of an accomplishment.
Also this is petty but his younger look is kinda goofy, where's my GILF skin Koei.

To summarise: Do I like this pass more than the first one? Mostly yeah. Land of Wano (CP1's last pack) is my favourite of the DLCs, but the 2nd/3rd/4th place slots are occupied entirely by CP2. The rise in quality is just absurd, in part because these characters are less obviously cut from the base roster to be sold later.

I would say "here's to more DLC", but I think this game is finished. It's been a great run all things considered, so here's to a PW5 that hopefully BRINGS BACK KUMA WHY DID YOU CUT HIM YOU MANIACS-

[Writer was dragged off stage.]