Laravel ORM filter with many to many relationship

I'm building a search by company and/or category. The output should be listing companies, each & every company output with 1 or more categories.

Example output to achieve:

1. Company 1, (category 1, category 2,...)
2. Company 2, (Category 1, category...) ...

Company entry about 20k rows while categories 1k+ rows.

this query taking too long time & eat up processors as well.

$companies = Companies
        ::with(['categories'=>function($q)use($category){
            if (isset($category)){
                $q->where('slug','=',$category->slug);
            }
        }])->paginate(20);

While this query, only filter the category inside the company modal.

$companies = Companies::whereHas('categories',function($q)use($category){
            $q->where('categories.id','=',$category->id);
        })
        ->paginate(20);

With 2 modals

Companies

public function categories(){
    return $this->belongsToMany('App\Models\Categories','companies_categories','company_id','category_id');
}

Categories

public function companies(){
    return $this->belongsToMany('App\Models\Companies','companies_categories','category_id','company_id');
}

via Chebli Mohamed