Quarto blog rendering behaviour

I have started a blog using Quarto and it all seems to work. What I don't seem to have an intuitive understanding of though, is how rendering works in RStudio (I understand about freeze = true).
What do I need to re-render if I'm adding a post or making a change to an existing post?
Obviously the index.qmd file for that post, but do I also need to re-render the main index.qmd?
If I make a change in the _quarto.yml or _metadat.yml files, do I need to go back and re-render every posts index.qmd for the .yml file changes to propagate across all posts? (I get the feeling I do). If so, is there a 'render entire website' type command in RStudio that can be used?