I researched on PowerApps Office365Outlook.SendEmail/Office365Outlook.SendEmailV2 limitations but I haven't found anything related to PowerApps Send Email limitations .
and I can find the limitations for power automate send email that "Send an email notification (V3) action it can only send 100 emails in any 24 hour period. So it will take many days to send 1000 emails. If you use the Send an email (V2) action or the Send an Email from a Shared Mailbox it can send 900 emails every 60 seconds."
but for PowerApps Office365Outlook.SendEmail/V2 and SMTP, I haven't found anything related to limitations.