In reply to Marc.

That's going to be on a case-by-case basis. Some kits, such as the SaaSy one linked in the post, do not require the Elementor Pro upgrade. However, others will. My guess is that kit designers will want to utilize more features and will opt for primarily designing for Pro.

It is also possible kits may require other plugins. You will need to check the requirements for any that you are looking at.