[CSP3] reflected XSS directive

Hello
I saw at the OWASP the reflected XSS directive for the CSP header (site: https://owasp.org/www-project-secure-headers/#content-security-policy),
but I couldn't find this directive at your site.
Is this directive still in use?
In our company, we want to better implement the CSP header,
but we don't want to cancel the X-XSS-Protection<https://owasp.org/www-project-secure-headers/#x-xss-protection> header from older browsers compatibility reasons.
We use the X-XSS-Protection<https://owasp.org/www-project-secure-headers/#x-xss-protection> header as follow: 1; mode=block.
Is it possible using both headers together without them conflicting?
If the headers do conflict, which policy is stronger?

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