Jsaon, I don't think you need to do anything with the PR portal if you aren't leaving the airport. I'm not sure how connecting flights work because I do recall in the past you had to get your bags? But we did leave the airport and that was when they check the QR code we got from the portal.

As far as testing, going to the US, the Ellume home test is another that is accepted for entry. We ended up using that for the PR portal and it worked fine there too.