ensure redirected domains redirect through a canonical redirect and this too has any chains minimised, although BE SURE to audit the backlink profile for any redirects you point at a page as with reward comes punishment if those backlinks are toxic (another example of Google opening up the war that is technical seo on a front that isn’t, and in fact is converse, to building backlinks to your site).
After a while, Google will know about your pages, and keep the ones it deems ‘useful’ – pages with original content, or pages with a lot of links to them. The rest will be de-indexed. Be careful – too many low-quality pages on your site will impact your overall site performance in Google. Google is on record talking about good and bad ratios of quality content to low-quality content.
An SEO audit should not be rushed. It simply takes time to uncover root causes of the issues affecting your online health. Depending on the size of your site, a proper audit can take anywhere from 2-6 weeks to complete. Due diligence is required when making major changes to any website, and an SEO specialist must conduct a thorough investigation to make accurate, impactful recommendations.