Keeping in mind that I am (a) old process, (b) still waiting for final approval and payment … here’s what I’ve seen from others:
So it first moves to “Transferido SIISEF” when paying at biometrics (new process) >>> seems so, yes:
then “Candidatura Aceite” at some point before the card is shipped? >>> hard to say. Maybe someone who’s actually been approved/got their card can chime in?
It’s also possible “Candidatura Aceite” is only used for old-process applicants to mean “pre-approval,” but I got through Biometrics and am now in “Transferido SIISEF” without ever being in “Candidatura Aceite.” 
I have seen some (old process, 2021 application) cases whose final DUC is being generated this year (“Aguarda Emissão” - so obviously they’ve got Final Approval) yet their top-line status is still “Transferido SIISEF”
Does the portal show the date for the last status change? >>> Main status, no. The billing tab does list issue dates for DUCs however.