Got new pacnew files for these .json files

I got new pacnew files for /etc/tpm2-tss/fapi-profiles/P_ECCP384SHA384.json and /etc/tpm2-tss/fapi-profiles/P_RSA3072SHA384.json. Should I paste the content of the new pacnew files into the non-pacnew files, before deleting the pacnew files, or should I do something else? I can post the content of these files if needed.

So, I should just put the content of the pacnew files instead of the non-pacnew files, right?

Yes - you should be fine to replace the content in the original files with the content in the .pacnew files.

Generally, you are meant to decide this for yourself. The theory is that only you will know if there is anything that should be kept.

That said, you could always save a copy of the original before doing anything; for example:

cp P_ECCP384SHA384.json P_ECCP384SHA384.json.bak

and then go ahead and replace the file with the pacnew, and reboot as needed. If there is any major issue, the original can still be reinstated:

cp P_ECCP384SHA384.json.bak P_ECCP384SHA384.json

Again, these are only examples.