Using hooks for additions and overrides is recommended. You could also override templates the regular way, by adding “header.php”, “page.php” etc to your child theme folder.

Why should I consider using hooks instead of template overrides?

Two obvious reasons:

1. If you’re just going to do a tiny tweak, it is just easier.  Check out available actions, available filters and pluggable functions
2. If you want to change, remove or add something to the output of for example the post feed, you will benefit from Express 2 doing the same action on all post feeds: Search results, archive, front page posts and so on. Easier than overriding all those templates.