Integrate SP Page Builder into the template

As you know, Travelami is one of the templates completely not based on SP Page Builder component because it's built fully with Astroid's layout builder thanks to the awesome collection of Astroid widgets.

Can I install SP Page Builder to run with the template?

Yes, you can. If you're not interested in building the content with Astroid widgets, you can integrate SP Page Builder with the template and build your pages properly.