They're going to disguise themselves as Chantry scholars who have been excommunicated (or just silenced and had their research heavily suppressed, if the Chantry doesn't do excommunication? unsure.) for their hot takes on rifts. They'll concoct some plausible academic conspiracy theory nonsense in advance, with help from some magic nerds if necessary, and they can use Bastien's printing press to produce some materials that look like genuine efforts to publish papers.

Their initial approach to the secure archives will be to attempt to get in using their identities.

Their initial approach to Nastasia Sellic will be to try checking wherever she is staying/living to see whether she has any written notes or records of what was censored, as well as using the sending crystal bug to listen in and see if she mentions anything further about her ideas and/or what she's into, personally, in case Richard has to seduce her (with Bastien's help).