I think that testimonials can be on both the sidebar and a full page. It doesn’t make sense to have more than one or two testimonials on a sidebar or a landing page, but having a massive page of testimonials can speak for your service quality. When it comes to the content of the testimonials, if you copy them from Google My Business, Yelp, or other directories, this is duplicate content. It might keep a page from ranking on (your brand name + reviews), but I doubt you would trip a Panda filter with it. Instead I recommend a much more sophisticated solution that looks at Net Promoter Score (NPS) where separate reviews can be collected and published.