What are the best practices for subdomains SEO?

I would love to read expert opinions and advice regarding following question about using and optimizing subdomains:

1. what are some effective strategies and techniques for optimizing subdomains to improve search engine visibility and rankings?

How can i ensure that each subdomain is properly optimized for relevant keywords and provides valuable content to users?

2. When using multiple subdomains, how does it impact website crawlability and indexing?

Are there any potential challenges or considerations I should be aware of? how can I ensure that search engine bots can efficiently access and index the content on each subdomain?

3. what are the potential risks or drawbacks of utilizing subdomains for seo purposes?

Are there any specific concerns related to domain authority, duplicate content, or keyword cannibalization that i should be mindful of? how can i mitigate these risks and maximize the benefits of using subdomains?

4. Are there any specific technical configurations or considerations that can enhance the SEO performance of subdomains?

what server and dns settings should i be aware of? how can I properly implement canonicalization, url structures, and structured data markup for subdomains to optimize their visibility in search engine results?

5. Are there any recommended tools or resources that can help me analyze and monitor the SEO performance of subdomains?

how can i track keyword rankings, organic traffic, and other important metrics specifically for subdomains? are there any best practices for reporting and analyzing seo data for subdomains?