How to use the Better Search Replace plugin

Hello guys,

I’ve enabled Cloudflare Flexible SSL and verified that my sites (https://proddigital.com.br and https://idiomas.proddigital.com.br) are loading all the content of the pages normally. Only a few elements seems to still load in http, so the green padlock does not appear in the address bar.

So I installed the Better Search Replace plugin, but I have questions on how to use it.
In the “Search for” field should I put the term http and in the “Replace with” field should I put the term https, correct? And as for the tables, should I activate them all, because after all, is it on the whole site that I should look up and replace http for https?

If it really is like I said above, then in case I put http lookup and replace to https, and select the “wp_posts” table, then the plugin will search all http terms only in URLs, or the plugin will also search and replace within the text?
I ask why, if it is to search and replace within the text of the post too, so if my site has posts talking about subject related to http, the plugin will replace with https, but this is wrong and should not happen.

Another question is … should I change the Site Address (URL), Siteurl and Home, from http to https. This process can I do with the plugin? If yes, then how to do this, and on which table should I select?

I thank you.
Rodrigo Carlos