Google Search is fine with using either subdomains or subdirectories. Making changes to a site’s URL structure tends to take a bit of time to settle down in Search.
Sitemap files are a great way to make your content known to Google and to other search engines. To handle large websites, you can generate more than one sitemap file per website. You can either submit these individually, for example, through a Google Search Console, or you can create a sitemap index file.
You could start out with a fresh domain that you’re registering, or you could try to buy a domain from someone else or from a registrar, please follow the below guidelines to avoid purchasing penalised or a spam domain.
Can they compete with Black Hat Websites? Can a website compete for high rankings using only white hat techniques? First of all, you always want to be making a white hat website, something that stand the test of time.