Eloquent nested query

I have 2 modules channels and users I want to return the users count when selecting a specific channel, so I made an eloquent relationship in channels model users() but the performance is a bit bad so I made a lot of googling and I ended up with using nested query. so how can I make something like this in laravel

// Model Relationship

 public function users()
    {
        return $this->belongsToMany(User::class, 'channel_user');
    }

// Channel Transformer
 public function transform(Channel $channel)
    {
        return [
            'code' => (string) $channel->code,
            'name' => (string) $channel->name,
        ];
    }

public function includeUsersCount($channel)
    {
        return $this->primitive($channel->users()->get()->count());
    }