Nice team! Before rating it, I'm gonna answer the questions you have first then suggest my changes.
Is Grass Knot the best coverage move on Thundurus-Therian for my team?
No. Ground-types aren't a burden as you're mono-flying. Secondly. there really isn't anything you miss out coverage on if not running that move (probably Landorus-T, etc. but Celesteela hard walls those).
On the other hand, stuff like Amoonguss, Ferrothorn, etc. hardwall Thunderbolt + any combo you're running. Therefore, hitting out coverage on these things, from another coverage move like Psychic or Focus Blast is better.
Thundurus-Therian (M) @ Heavy-Duty Boots
Ability: Volt Absorb
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Substitute / Agility
- Nasty Plot
- Thunderbolt
- Psychic / Focus Blast
Agility is an option that can completely maul faster teams, and so that nothing can easily revenge kill you. Also, I think Substitute is extremely sub-optimal (Celesteela already absorbs Toxic and other condition pretty well), so I think it can be replaced, too.
Does this team have a good matchup vs Tapu Koko?
If you play well around your Landorus-T and don't recklessly chip or sack it, it can pretty much deal with it at full HP. Offensive pivot set 3HKOes, so it's not a worry. However, Specs having a good chance to 2HKO means you're forced to play around Landorus-T/Thundurus-T and Celesteela which is a bit prediction reliant. Nevertheless, Flying-monotype can't have 100% confirmed way of confronting Tapu Koko.
252 SpA Tapu Koko Dazzling Gleam vs. 252 HP / 48 SpD Landorus-Therian: 120-142 (31.4 - 37.1%) -- 82.7% chance to 3HKO
252 SpA Choice Specs Tapu Koko Dazzling Gleam vs. 252 HP / 48 SpD Landorus-Therian: 178-211 (46.5 - 55.2%) -- 99.6% chance to 2HKO after Stealth Rock and Leftovers recovery
Should I replace a move on Dragonite for Roost?
Yes. In place of Extreme Speed imo, and use Dual Wingbeat over Outrage so you don't get victim of the choice lock that easily. Priority + Spe boosting sounds pretty weird, also since you're having a revenge killer.
Dragonite @ Heavy-Duty Boots
Ability: Multiscale
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant Nature
- Roost
- Earthquake
- Dual Wingbeat
- Dragon Dance
Should I use Thunderous Kick or Close Combat on Zapdos-Galar?
Obviously, Close Combat. Breaking power, especially with Scarf is better imo. Regardless, the defense drops don't really matter (sweepers are frail anyway, they care about OHKOing, not preserving bulk).
Updated Team after the changes answered
After the above questions, I think I have some changes to suggest .
Dragonite --> Corviknight
Corviknight @ Leftovers
Ability: Pressure
EVs: 252 HP / 252 Def / 4 SpD
Relaxed Nature
- Defog
- Body Press
- U-turn
- Roost
What the. This is my reaction when I see a mono-flying that has no Corviknight in it. Celesteela, just isn't taking the same role of it imo. It's dependent on Leech Seed for recovery, and it can't Defog. Meanwhile, this team has only Mantine for Defogging (and it loses to most Stealth Rocks setter). However, combining it with Corviknight forms a strong defensive Defog core.
Make Mantine Physically Defensive
Physically Defensive Mantine is the way to go. It's important because Urshifu-RS + Rain just kills this team very easily. Also, if you're looking at the Flying-type sample mono team, it is very similar to this team and has Phy Def Mantine, not SpD.
252 Atk Choice Band Urshifu-Rapid-Strike Close Combat vs. 248 HP / 164+ Def Mantine: 145-171 (38.8 - 45.8%) -- guaranteed 3HKO
Meanwhile your spread gets 2HKOed by Close Combat.
252 Atk Choice Band Urshifu-Rapid-Strike Close Combat vs. 248 HP / 0 Def Mantine: 197-232 (52.8 - 62.1%) -- guaranteed 2HKO
Anyways this thing doesn't need SpD Investment, it's already too bulky ;)
Final Team
Me has hoped that I helped :p
