Moving All Accounts to New Server Questions

Hey. I've got a task to handle and here's my full scenario. Any help would be much appreciated! A shared hosting plan managed with CPanel exists and now I need to move them to a new (more featured) hosting plan with CPanel in the same provider. The current hosting plan contains about 170 websites which are almost all static html-css websites except the 2 of them have their seperate databases. Each of the websites have their own directories in the hosting's public_html folder (one server, multiple websites) and each have their own domains (on different provider than my hosting provider) 1) Which one do I need to follow to achieve a seamless and relatively fast migration; A -) getting a full cpanel backup and then importing it to the new CPanel or B -) moving all files via SFTP and using PHPMyAdmin to handle those two databases? 2) How can I handle setting all of these 170 domains to match the new hosting package? (host files will be on the same hosting provider and I think this clearly shows I need to do more than changing the name servers, since they will be the same) 3) I need to get SSL sertificates for each of them with Let's Encrypt but the provider does not support the automated system so I need to manually do this, tips for also doing this would be awesome... Thank you so much!