Wow!! It is excellent. This series has been so well written. This isn't just another Trials and Tribble-ations kind of version of Balance of Terror though. I've been very critical of prequels that retcon the original material. The Disney+ series Obi Wan Kenobi is an example that rides roughshod over the original Star Wars movie with little regard for it at all.
This series doesn't just understand it's subject completely but adds value to it with every sentence. Despite Pike knowing his future; his terrible injury, and that he fails to save two cadets, we now see why he will not let that future be changed. It isn't just the Federation-Romulan War that would begin, but through the death of Spock, he would change the future is so many different ways, because Spock is so integral to so many different future events including the V'ger probe and the Vulcan-Romulan Unification.
We now can see why in The Menagerie parts 1 & 2 Spock is willing to mutiny to take Pike to Talos IV. Spock is reciprocating by laying down his career for the Captain who was injured so that he was not. And now we know why Pike keeps flashing those repeated "no" signals, because if Spock gives up his career for him, then his sacrifice will have been squandered, and his seven years of pain will have been in vain.
We also now know why Una Riley is not on Kirk's Enterprise and Spock is Number One. Her genetic modifications have been frequently established in Star Trek canon as being illegal, and it was only a matter of time before the law caught up with her.
However, it can be faithful to the original material and still give fan service, with the sheer layers of connections and references going on in both the real past and the alternative future i.e. Scotty on the communicator to Spock in the Jefferies Tube before he is injured.
