SEO competition and Keywords

Hello friends, I am trying to build a new website with English content. The website I am going to build will be related to a product promotion. However, I need your help with a few points;

Product's Main Site: www.vertshock.com Target Keyword: vert shock

What I need are long-tail keywords. I have found a few keywords related to this product. I would be very happy if you could suggest a few keywords as well.

When I look at the SEO competition level, I base it on the results produced by the “SeoQuake” extension. How accurate is it for me to do this?
Is the number of indexed pages appearing when we search for a keyword on Google directly proportional to the competition level?

For this product, I will have 10 articles of 500 words written using keywords “you suggest”. Will this be sufficient for the competition?