Hi! I just have a couple of suggestions.
First off, even though Toxapex is a fantastic singles Pokémon, I feel like it doesn’t fit in with your team, especially since haze will completely reset Sylveon’s Calm Mind. Plus, all the ground weaknesses on your team don’t allow your Garchomp to even carry earthquake. I feel like Gardevoir would be perfect for this spot, as telepathy makes it immune to earthquake and it has icy wind and a lot of other good support moves like screens (Although I wouldn’t recommend screens since you have Incineroar for Damage Reduction) and heal pulse to further help your team.
Next, Incineroar. Looks good, but I’d recommend Snarl over Bulk up as Incineroar likes to switch out often to cycle intimidates, and you have Wil-o-wisp and intimidate to deal with physical attackers already. If you wanted, you could give him an eject button to further cycling of intimidate + fake out, but that’s pretty gimmicky. Also, usually health berries are better in 4v4 because there are generally less turns to gain back health than in 6v6. You can also consider using Flare Blitz over Lariat to hit steel types that harm Sylveon.
Next, Garchomp. Good, I’d just say to add earthquake over poison jab or rock slide, and use Bright Powder and Sand Veil, which I’ll explain later.
On to Metagross. I feel like it could be a great “Glue” Pokémon for your team, having coverage for fairy, poison and ground types to cover your team’s weaknesses.
Metagross-Mega @ Metagrossite
Ability: Tough Claws
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Bullet Punch
- Zen Headbutt
- Ice Punch
- Protect
Ice Punch or Zen Headbutt could also be fighting coverage for other steel types.
Sylveon is solid, but modest or timid nature is probably preferred, and I’m going to change protect #2 to quick attack, which I’ll also explain later.
Finally, Gengar. It’s okay, but I’m not sure about it. If you really want to use it, go for protect over Focus Miss and give it a Z-Move as this team doesn’t have one, but there is a mega already, but I’d recommend Tyranitar. It feels really good on this team. You can Sand Veil + Bright Powder cheese with Garchomp, plus sweep with weakness policy! Sylveon’s Pixilated Quick Attack and Draining Kiss on Gardevoir will allow for a late-game sweep.
Tyranitar @ Weakness Policy
Ability: Sand Stream
EVs: 252 HP / 252 Atk / 4 SpD
Adamant Nature
- Rock Slide
- Crunch
- Protect
- Fire Punch
Fire punch can be any coverage move. You could also use Rock Polis and a faster Spread for even more potent sweeping, but make sure that Gardevoir is always faster to proc weakness policy first.
PokePaste
Sorry that I went all out of order. I hope that I didn’t change too much and that my suggestions help!