This section has yet to be updated to the new, expanded and more detailed interface, but the list itself is correct and should still be of use.
Here’s that second Original Series pilot Lucille Ball fought for, now with (most) of the classic 1960’s Star Trek crew. Still no Dr. McCoy, Uhura, or Chekov, Kirk has a different middle initial, the uniforms and sets still aren’t quite right… but we are for the first time recognizably in the world of the show that started it all.
Just to clarify - the original Star Trek will appear less advanced in terms of its designs and aesthetic compared to the other Star Trek shows we have watched so far, but this is only due to the limitations of television production at the time. This is not “true” in story terms - the technology and society in TOS should be read as on par with Discovery and Strange New Worlds, which all take place at roughly this point in the timeline, and the Enterprise, despite looking different, should be accepted as the exact same ship Pike commanded in Strange New Worlds.
As for the actual viewing order, to fully appreciate the development of the show, it's recommended to watch TOS in production order instead of by air date. In general, don’t get too hung up on continuity with the rest of the franchise in these early days - they take quite a while to pin some stuff down that the rest of the franchise takes for granted.
The Menagerie is largely reedited from The Cage, which we watched a while back, but don’t skip it - after spending so much time with Spock and Pike since, this episode is absolutely essential.
Next we revisit SNW’s season 1 finale, “A Quality of Mercy”, and see how differently events play out with Kirk in command of the Enterprise.
While Mirror, Mirror is the episode that first introduces the Mirror universe, we’ve already been there on Discovery. Enterprise had a two-part episode there too, actually, but that’s one of the ones we skipped for later viewing and will be arriving at shortly.