The other answer is very good already, I just thought it would be helpful to break down the common teammates to these cores because it always helps me to know each Pokemon's specific role within the team.
This team is basic Hyper-Offense: built around a super-powerful Pokemon, Porygon-Z.
-Porygon-Z: super powerful with basically 3 turns of essentially adaptability boosted Hyper Beam without drawbacks, the goal is to Dynamax Turn 1 and dish out huge damage.
-Clefairy: Support for Porygon-Z. Can reduce or redirect damage from P-Z with Friend Guard/Follow Me, plus boost its damage output even further.
-Talonflame: If redirection is not needed, Talonflame allows great speed control with priority tailwind plus quick guard, allowing Porygon-Z to move before all of its opponents.
-Dracovish: works really well with Talonflame and fits the Hyper-offense mode.
-Chandelure: The Anti-Trick Room Pokemon, which this team would struggle with otherwise.
-Rotom-Mow: Just a basic Special Attacker. It doesn't really have a defined role, just some good coverage.
Usually the game plan for this team is to lead Clefairy plus Porygon-Z with Talonflame and Dracovish in the back. Let Clefairy go down with follow me when the time is right and bring in Talonflame to set tailwind. Try and remove Dracovish counters like Gastrodon because Dracovish in tailwind is your win condition. Lead Chandelure against Trick Room teams.
Beat Up Teams
Another form of Hyper-Offense that just requires some setup.
-Sneasel: The focal point of the team. Provides setup and support for the two main sweepers, Coalossal and Cobalion.
-Cobalion: The Justified Pokemon. Pretty self-explanatory, try and beat up Cobalion with Sneasel and start dishing out lots of damage.
-Coalossal: Using surf doubles its attack and maximizes its speed. Gmax Volcalith is a very strong effect.
-Gastrodon: Help against water types that threaten Coalossal. You can also surf into Gastrodon to boost its special attack, but this is not the primary goal of the team.
-Sylveon: Basic late-game cleaner and good coverage.
-Dusclops: Anti Trick Room, pretty self explanatory.
Usually the game plan for this team is to lead with Coalossal and Sneasel with Gastrodon and Cobalion in the back. Surf into Coalossal turn one, then if it is not needed for taunt support switch it out into Gastro to preserve fake out/beat up for late game. Cobalion/Sneasel/Gastrodon/Sylveon is also strong. Against trick room, lead dusclops and either Sylveon or Gastrodon with Cobalion and Sneasel in the back to get rid of the trick room setter and clear the way for a late game beat up and dynamax.
I found all the rental teams here. Have fun with VGC!