Best way to handle multiple landing pages?

I’m trying to figure out the best way to handle a site in which there will be multiple landing pages using a different theme or template. The landing pages will be single sales pages with a call-to-action that are accessed via a Google ad or some other paid search, but not directly linked elsewhere. I’m not sure if a multisite would be best, since there will maybe be different themes and widgets in action, or if using the same install as the main site and using templates, as I’d like the landing pages to reside on the same domain (e.g. https://my-site.com/landing-page/this-is-one-of-them).

Any advice is greatly appreciated — thanks!