What is the difference between purchasing a template vs. buying a plan?

Hello, I am just starting with webflow and I was wondering if purchasing a template gives the me the same benefits as purchasing a site plan? Or do I need to buy a site plan no matter if I use a free or paid template? For example, if I am on the free plan, and I purchase a template, does this let me publish a site with custom code (which I need)? Or do I need the site plan to allow custom code on any template, no matter if free or paid?

Also unrelated but interested; how can I get my domain from Wordpress over to here? I just want the domain, not the whole site.

Thank you in advance!!