There are some free tools that I can recommend here is HubSpot’s Blog Topic Generator, Hemingway Editor, Piktochart, KingSumo Headlines. Also, I don't believe any tool gives you accurate data but certainly, you can get an idea to use data for future reference.
As I have experience with few tools for content quality checker are here: Grammarly, Small SEO tool and Copyscape tool.
I'm a blogger myself and content is at the center of my livelihood to drive sales and commissions. I use Grammarly and it comes with all the features you need for creating good copy - grammar check, plagiarism check, and correctness check.
Apart from this, I use Surfer Pro to optimize my articles for SEO.
Quality content always matters for the effective internet marketing strategies and it’s an awesome feature to create a huge online impression.
You can find huge sources over the internet where you can get the quality score of your content but I strongly recommend Grammarly and Copyscape tool. They are the best in the industry and you can check the best quality of content through these tools.
Small Seo Tools is also the best option to check plagiarism.
If you would like to know more assistance, please let me know.