Hi @jdeyla and welcome on the forum
Yes, RGAA 4 and WCAG 2.1 do match.
RGAA (wich stands for Référentiel Général d’Amélioration de l’Accessibilité, i.e. Accessibility Enhacement General Referential) is designed and built to match WCAG 2.1.
This is by design, as RGAA is an element of the French law. To be more precise, the French law had to implement the European directive, that asks to be compliant with WCAG; RGAA is the technical part of the answer.
Moreover, in RGAA 4 for each criteria you will find the equivalent WCAG techniques and success criteria (and even the reference to the European directive details). For example, go to criteria 1.1, expand it, and look at the botom of the section (just above 1.2 so).
So feel free to use it confidently.
Hope this helps