When the crew is discussing their plan to access the Artifact, Picard's arms are folded, in the shots from behind. In the shots from the front, his arms are down by his side.
In the opening, Picard views a picture on the computer screen of himself as Locutus. He then touches the right side of his face as if to remember his Borg implants. Locutus had Borg implants on the left side of his face, just as the computer screen was showing.
This is a reflection in the computer monitor.
This is a reflection in the computer monitor.
In attempting to gain Soji's trust, Picard tells her to look at the dilation of his pupils and to listen to the timbre of his voice and the fluctuations of his heartbeat. As mentioned a few scenes earlier, Picard's heart is artificial (and has been since his days in the Academy) and would therefor not be subject to fluctuation based on mood.
However, even although his heart is artificial, it is very sophisticated and its rate can presumably vary to accommodate the physical or emotional demands and their concomitant changes in blood flow.
Despite the advanced state of mental health care shown in the other 24th century Star Trek shows, including Picard's experiences in Star Trek: The Next Generation (1987) and Star Trek: First Contact (1996), Borg biotechnology remains far in advances of the Federation's. Assimilation infiltrates every aspect of a person's being and Federation psychotherapy clearly cannot 'cure' it completely, as seen in the behavior of Seven of Nine and other recovered Borg. Moreover, Picard's nightmare's and flashbacks are perfectly consistent with his similar traumas in First Contact.
After the opening of the box, Soji begins coughing before the gas cloud reaches her, showing a synchronization issue between the live action footage and the CGI gas.
After the Romulans place heavy restrictions on what Picard may or may not do during his visit to The Artifact, he is transported to a completely empty chamber with nobody there to guard or welcome him, then allowed to wander about on his own.
The spatial trajector that Picard and Soji use to escape is a long-range transporter, said to usually be reserved for use by the Borg Queen. In Star Trek: First Contact (1996) and several seasons of Star Trek: Voyager (1995), it is established that the Queen can survive the death of her physical body. She might be the only one aboard a Borg ship who wouldn't need a physical means of escape.