QUOTE: “The preferred domain is the one that you would liked used to index your site’s pages (sometimes this is referred to as the canonical domain). Links may point to your site using both the www and non-www versions of the URL (for instance, http://www.example.com and http://example.com). The preferred domain is the version that you want used for your site in the search results.” Google, 2018
The more important concept to keep in mind is that you want to choose keywords that best relate to the content present on a web page and on a website; if you don't have a dog food comparison matrix, then don't bother including comparison-related keywords; you are misleading your users, and certainly not fooling Google. So in an ideal world, you do have a comparison section, a reviews section, and a rankings section, housed on different pages or sections of your site, with each one tagged with the appropriate keywords. Correspondingly, your SEO and PPC search engine marketing efforts should that content by driving review keywords to the review pages and so on.
One thing Google has indicated it likes to do is penalize sites or stores or companies that consistently have poor reviews, so if you have many poor reviews, in time Google is going to figure out not to show your site in their rankings because Google doesn’t want to show those sites to their searchers. So prove to Google’s algorithm that you are trustworthy. Get other highly authoritative websites to link to you. Get newspaper articles, get industry links, get other trusted sites to link to you: partners, vendors, happy customers—get them to link to your website to show that you are highly credible and trustworthy.
QUOTE: “To summarize, a lack of helpful SC may be a reason for a Low quality rating, depending on the purpose of the page and the type of website. We have different standards for small websites which exist to serve their communities versus large websites with a large volume of webpages and content. For some types of “webpages,” such as PDFs and JPEG files, we expect no SC at all.” Google Search Quality Evaluator Guidelines 2017

Companies that employ overly aggressive techniques can get their client websites banned from the search results. In 2005, the Wall Street Journal reported on a company, Traffic Power, which allegedly used high-risk techniques and failed to disclose those risks to its clients.[15] Wired magazine reported that the same company sued blogger and SEO Aaron Wall for writing about the ban.[16] Google's Matt Cutts later confirmed that Google did in fact ban Traffic Power and some of its clients.[17]

Basically, SEO keyword research should be an ongoing and ever-evolving part of your job as a marketer. Old keywords need to be reevaluated periodically, and high-volume, competitive keywords (or “head” keywords, as opposed to long-tailed keywords) can often be usefully replaced or augmented with longer, more specific phrases designed not to bring in just any visitor but exactly the right visitors. (Who visits your site – particularly if they’re people who are actively looking for your services – is at least as important as how many people visit.)