Different posts_per_page on index and archive pages

Hi all,

I’m creating a custom theme from scratch and all is going well so far.

I would like to have a different value for posts_per_page for the index page, tags page and archive page. Currently, in package.json I have set posts_per_page to 5 which is what I want for the index. However, I would like to to show 20 posts on the tags page I am writing. Is there a way to do this? Is there a setting in package.json I’m missing?