The other answer is all good but only compares Kyogre with Primal Kyogre and doesn't go in-depth into Primal Groudon, so I wanted to add something more to it.
Kyogre @ Life Orb
Ability: Drizzle
EVs: 4 Def / 252 SpA / 252 Spe
Modest Nature
- Origin Pulse
- Ice Beam
- Calm Mind
- Hidden Power [Ground]
As we know how threatening this Kyogre set is, it's not real heat at the moment. I asked Lotiasite, who's a AG moderator about how much good it is, and he told me that it's not that great with CM WaterCeus running everywhere.
Since Kyogre can't fit Thunder, WaterCeus can set-up its own Calm Mind in front of you. And since you don't have recovery of any kind, even if you Dynamax it just outlasts you with Recover and wins the game.
+1 252+ SpA Life Orb Kyogre Max Airstream vs. +1 252 HP / 0 SpD Arceus-Water: 162-192 (36.4 - 43.2%) -- guaranteed 3HKO
So therefore, this fish is not the hot take for a Water-type sadly.
Arceus-Water @ Splash Plate
Ability: Multitype
EVs: 252 HP / 4 SpA / 252 Spe
Timid Nature
IVs: 0 Atk
- Calm Mind
- Judgment
- Ice Beam / Grass Knot
- Recover
This is the real take for a bulky CM user. Unlike Kyogre, it does not need the Spe, which is compensated by higher natural bulk and overall better speed. CM WaterCeus is pretty self explanatory, with the third slot is for hitting MRay, Eternatus or Grass Knot for Kyogre and other WaterCeuses.
What about big Land daddy Groudon-Primal?
Big Land daddy has also been irritated for a long time by another Arceus forme, GroundCeus. Both of the Calm Mind and Swords Dance set are able to compete with it immensely, which is why its viability offensively has decreased. Still, it's nonetheless a good counter to Zacian-Crowned and a soft check to Xerneas defensively. With Stealth Rock setter, it frees another DD slot on Dusk Mane Necro.
Groudon-Primal @ Red Orb
Ability: Desolate Land
EVs: 252 HP / 252 Def / 4 SpD
Impish Nature
- Precipice Blades
- Rest / Stealth Rock
- Sleep Talk / Stone Edge
- Toxic / Swords Dance
With a RestTalk set, it's absolutely hard countering the Sword Dog. SD sets are still good as ever, though you should use GroundCeus which is better now offensively.
Arceus-Ground @ Earth Plate
Ability: Multitype
EVs: 120 HP / 252 Atk / 136 Spe
Jolly Nature
- Swords Dance
- Substitute / Recover
- Earthquake
- Stone Edge
Arceus-Ground @ Earth Plate
Ability: Multitype
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Calm Mind
- Recover
- Ancient Power / Ice Beam
- Judgment
Thanks to solid coverage and having both EdgeQuake and BoltBeam combo, both SD and CM sets are threatening. Ancient Power hits Ho-oh so it can't whirlwind, while Ice beam takes MRay by surprise.
Tl;dr use WaterCeus instead of Kyogre and PDon is still good defensively, but GroundCeus is also a good pick for offensive roles.
Hope this helps!