I read this article at medium https://medium.com/lyfepedia/sending-emails-with-gmail-api-and-python-49474e32c81f about sending emails with the google api, but i wonder if i need a g suite account for that?
You can use Oauth2 to authenticate your application and use the Gmail api, note verification of a gmail application is not cheep and you will probably not be able to run it very long unverified.
Service account authentication is only possible using gsuite domain wide delegation and will only work on the domain email accounts. There is no way to use service account authentication with a normal gmail account.
Depending upon what you are doing you might want to look into going though the smtp imap server rather than the gmail api.