Overall I think the Pokemon on this team are all good. But the sets and items need some work so that’s what I’m going to address in this answer.
Slither Wing
Change Earthquake to protect as earthquake doesnt hit much in the meta rn and protect is more useful than earthquake anyway. I’d also suggest you switch either Cc or flare blitz for something like U-Turn so that you can use more fist impressions and have less move overlap with korraidon. U turn also lets you hit Farigiraf hard so that’s nice.
Flutter Mane
Dont try to make this thing bulky. Even with max bulk investment it’s still quite frail. Change rocky helmet to focus sash so you can live a hit and change the Tera to either Fairy for more dammage or normal Tera to help deal with Calyrex. Change the bulk investment to special attack as you don’t need the bulk investment. I’d also suggest you consider using icy wind or another attacking move over helping hand as Flutter does so much damage it’s kinda a waste to use helping hand on it.
Korraidon
Your current set is ok but I think a more bulky Korraidon would work better on this team so you can re set sun later in the game. The set I’d suggest is
Korraidon @ Clear amulet
Ability: Orachalcum pulse
Tera: Fire
Evs: 252 Hp / 252 Atk / 4 Spe
Nature: Adamant
-Flame charge
-Colision Corse
-Flare Blitz
-protect
This set gives more bulk and a better defensive Tera. Dont use Cc Korraidon unless your using the life orb set. Flame change is used so you can outspeed things like Calyrex shadow and max speed raidons. Flare blitz offers massive dammage when paired with Tera fire.
Raging Bolt
You already have so much fire type coverage so whether ball is kinda redundant. I’d use thunder bolt over wether ball and now that you have a consistent stab you can use Draco meteor over dragon pulse for a powerful nuke.
Calyrex
Choice specs is an interesting item choice on Calyrex but I think it can work. Drop dark pulse as it’s not useful when you have Astral barrage as an option. Instead use trick so you can potentially cripple one of the opposing Pokemon. Giga drain is also not a very useful move as even when it’s super effective astral barrage still hits harder. I’d suggest you try another move like substitute (for after you have tricked the opponent your specs) or something like will o wisp.
Whimsicott
Set is ok just switch the item for covert cloak so uour immune to fake out and change the Tera to dark so you can be immune to enemy prankster Pokemon. Also use Moonblast over energy ball as energy ball doesnt hit much in the current meta and with moonblast you have the potential to lower opponents special attack which can be a big problem for opponents if they ignore whimsicott.
