An enjoyable episode, though this one is definitely more about building the plotlines than advancing them.
We have confirmation of Laris and Zhaban's Tal Shiar origins (with no need to read the comics

), with Laris getting to show off her forensic skills.
And apparently, the Romulans have their own version of Section 31, except that instead of protecting them from outside threats, the Zhat Vash protect them from robots. And apparently have done so for "thousands upon thousands of years." That's particularly intriguing, since the Romulans only split off from the Vulcans around 2000 years before the in-series present day. A slip of the tongue/script? Or do the Zhat Vash have their origins in ancient Vulcan culture?
So, clearly the Zhat Vash jump to the top of the suspect pool for the Mars attack - they have the motive, and they're zealous enough that they might not care that it costs Romulan lives. However, here's a scary alternative: What if there really is something out there that the Zhat Vash have good reason to fear, and that something is what overrode the androids?
Minor continuity note: The version of the NCC-1701 Enterprise briefly visible as a hologram in the Starfleet HQ lobby is the same one used in Star Trek Discovery.
According to the chalkboard on the Borg cube (or Borg Artifact Research Institute), it's been sixteen years since the last time someone got assimilated - and yet they still don't feel comfortable enough to stick an electronic counter up there. Kinda feel sorry for whoever has to keep re-writing it every day.
But it does at least give us a timeline. This facility has been around a long time - since well before the supernova, in fact. That makes sense if the backstory from the Abrams Trek movie is true, about Nero's mining ship having been retrofitted with Borg tech. There is a reference to the Romulans being its 'current' owners - could it have changed hands at some point?
The Romulans' reclamation of the former Borg appears to be motivated more towards the acquisition and selling of their cybernetic implants than any altruistic feeling towards the organic hosts. Their work here jars with the earlier reference to the Romulans not doing any research into cybernetics (which is highlighted - Narek says the place doesn't feel very Romulan), but then again, perhaps that's why they need so many outside experts.
Notably, Soji, like Dahj, has secured herself a place in the forefront of research into artificial beings. Deliberate? Or merely the result of innate aptitudes and interests?
The heirarchies between Narek, Rizzo and Commodore Oh seem interesting. Oh clearly considers herself in charge, but Rizzo seems to view her more as an ally of convenience than a superior. Perhaps Oh is higher ranking within the Tal Shiar, but Rizzo and Narek are deeper inside the Zhat Vash.