I have very mixed opinions about this one. I quite liked the A plot. The cubes vs orbs might not be the most original idea, but I liked it and thought it was integrated well into the show. They had a lot of good lines to give them and they were fun. The moment I saw the destroyed room though, I assumed immediately it was a Romeo and Juliet plot, so I wasn't surprised at the conclusion. I did think that Olly was going to have an "Okana" role where she was secretly helping the young couple hide from their parents, but the reveal that her electrical powers were getting in the way of being an effective engineer. Not a bad plotline.
On the other hand, I really did not like the B plot. One of my big criticisms of the earlier seasons is that there was just too many zany antics going on without really any depth to it. While the A plot still had that chaotic energy, we still get to see how Mariner has improved as an officer. With the Boimler plot, it just felt wacky and superficial. It's been in the back of my mind all season that while Mariner and Boimler typically share equal spotlight, he really has taken a back seat this season. He hasn't really had an A plot himself, and his arc is seemingly going to be about comparing himself to Alt!Boimler. That's something early season Boimler would definitely have struggled with, so it's almost like he's regressing in a way. I suspect in the finale he'll learn to embrace himself, but I honestly wonder if the next four episodes will just be all Mariner-centric. They've done a good job with her development, but with this being the last season, I think a lot of us would like to see her in a good place with her responsibilities and him in a good place with his self-confidence, and this arc isn't getting us there.