Hi, I am Dave, I will help you with this.
Whether you us a 3rd party anti-virus is really a personal choice.
Windows Security is a full security suite that is on a par with all the paid for 3rd party Anti-virus suites, it is highly rated.
Windows Security has many components like Defender, Ransomware Protection, Memory Integrity, Core Isolation...etc. and its Virus Definitions are updated regularly like all the 3rd party anti-virus suites to include any newly found malware on the web.
Defender is tightly integrated with Windows, it is free and will not slow down your PC like many of the 3d party anti-virus suites.