Contextual advertising is advertising that you see for specific

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SEO is aimed at organic search engine ranking of your website for a specific query. The user types their query into the search engine and receives a list of websites.

This does not mean that your website will fly to the top for all queries in your niche. For example, you install plastic windows. An SEO specialist worked on the website for several months and managed to move to the top for queries such as “install plastic windows” and “plastic windows Voronezh”. His success in promotion does not mean that your website will be at the top for all queries about plastic windows.
There is a version that Yandex and Google do not like sites on constructors and index them poorly. Technical inflexibility and code redundancy prevent systematically setting up organic promotion, but in many ways it also depends on the niche. In high-frequency niches with a site on a constructor, you really will not get to the top, it is better for you to make a custom site.

If you have, for example, a store with bags made of tunisia mobile database plastic caught in the ocean, or you sell plumbing for doll houses, then with a site on Tilda and competent SEO promotion you will quite easily get to the top positions.
Support
Here, a site on a constructor comes out ahead with a huge plus. You can independently change information and photos, add new products and services and not worry that the section will float or the page will stop opening. As a rule, for sites on constructors, monthly technical support, unless you want to make global changes - add a new section, for example.

To work on the site from scratch, you will need to arrange technical support, since the range of independent actions is limited. You yourself will be able to change the text, perhaps.