“I use my company email (firstname.lastname@example.org) for subscription accounts (e.g. Quickbooks, Linkedin, etc.), newsletters (e.g. trade journals, industry blogs, etc.), and Google Alerts (www.google.com/alerts to monitor the web for interesting new content related to your work). Will these be affected by the migration from a Microsoft based email system to mail on G Suite?"
SHORT ANSWER: No :)
SAME EMAIL ADDRESS: Your company email address (email@example.com) is staying the same and not changing. Therefore, if your subscriptions are tied to your company address, nothing will change and you will continue to get emails in your inbox.