HTML markup best practices

I am learning ionic and it has been very smooth sailing. However, I have so far not found any article on recommended practices for HTML markups.

Can I use any valid HTML markup in my templates ? Such as markup for SEO, and ARIA attributes.

Do some markup break the web components ?

Can you please post a link to an article like that ? Specifically, I am looking for “Best practices”.

Found the first one, I could not place ion-header inside a component. Understood the meaning of three root elements in the documentation now