You can use Acronym's Google Tag (gtag) extension to implement GA4. Refer to the documentation linked from the extension to learn how to set it up properly.
In terms of correctness, assuming that you have existing implementation for Universal Analytics in Launch, then you should perform a 1-to-1 replacement with a corresponding GA4 implementation.
If you have performed that 1-to-1 replacement already and have verified that all GA4 tags are firing correctly, then any data discrepancies that you discover may be because of measurement differences between Universal Analytics and GA4 that are due to the differences between those 2 products.
Good luck.