Leadpages, Convertkit, mailchimp – how to best connect my freebie and tie it to an automatically generated email?

Hi! I created a coming soon page on my site (using Squarespace) and created a freebie workbook on Canva which I plan to place on my coming soon page to collect email opt ins while I complete the rest of the website. I’m learning how to do this all along the way. I could use some guidance on how to or what system automatically generates email to people who opt in using the form on my website. For example, does mailchimp do this if I connect it to my opt in form? What is convertkit and leadpages and how do they differ from mailchimp? My goal is to put in place systems that generate things on automatic from the start so I can continue to work on content creation and other places in my business. I greatly appreciate your assistance. Thanks!