Thank you for posting your query on Q&A.
To answer your question yes, if you have configuring conditional access in Entra ID, The default security settings will be turned off and apply your conditional access.
If you have already configured conditional access in Entra ID, the Security defaults will not be turned on.
I hope this answer helps! If you have any further questions, please feel free to ask.
Reference: https://learn.microsoft.com/en-us/microsoft-365/business-premium/m365bp-turn-on-mfa?view=o365-worldwide&tabs=secdefaults
https://learn.microsoft.com/en-us/entra/fundamentals/security-defaults
Thanks,
Akhilesh.
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