Sylveon
Consider swapping yawn or wish for Mystical fire to not get walled by Steel types. Otherwise good.
Claydol
Entry hazards are not to good in VGC due to the less switching so try replacing it with ally switch, which most people might not expect and if predicted correctly it gives your other pokemon a chance to do whatever it wants.
Gyarados
Intimidate is a better ability here because you can already boost attack with dragon dance and intimidate lowers both the opponents to make them weaker. However if you do want to run moxie then remember to dynamax this Gyarados to have a better chance at getting a moxie boost. You can also replace Ice Fang with Bounce into Max Airstream to raise speed.
Rotom-Heat
Not much to do here, its good.
Dragapult
This is good but have you considered swapping U-Turn for Thunderbolt? Thunderbolt hits Togekiss which would otherwise hit your team very hard. Choice Specs is also an option.
Ferrothorn
I think an Occa Berry might work well due to its 4x weakness to fire which seems popular these days. Also you can try using Iron Defense which may sound gimmicky but perhaps you make it a specially defensive in EVs and then use Iron Defense to increase Physical tankiness. But an attacker also works well.
