Hello,
What I mean is that the regular Paypal plugin is quite old, and maybe will continue to be supported, but maybe the Paypal support can can give you information on this specific point.
Each paypal plugin often leads to merchant accounts with specific settings for each Paypal plugins.
So logically Paypal support should be able to tell you if your merchant account needs to evolve, which will give good clues on what to do next.
And just in case the Paypal Checkout plugin is the most recent Paypal plugin we develop and is up to date (and with last 3D secure standards).
Regards