In Google Workspace, you can use GAS (Google Apps Script) to achieve advanced processing. Here are some examples of how to use GAS.
Use BroadcastMails (spreadsheet) and BroadcastMails_Template (document) to send out emails with the same content to many individual addresses.
If you want to specify individual attachments, please use BroadcastMails_PrivateAttachments (spreadsheet).
See BroadcastMails_Manual (PDF) below for more information.