Minor spoilers, I'll try not to give too much away.
- Episode 2, Bête Noire, the episode ends in a positive note, but is more in the weird category in terms of endings.
- Episode 3, Hotel Reverie, generally ends on a happy note however it has a lot of sad moments within the episode.
- Episode 5, Eulogy, is probably the saddest episode of the season. It's also arguably the best. The ending I think is a positive one. It's a general theme of loss and closure.
- Episode 6, USS Callister: Into Infinity, I think of you found the first USS Callister episode to end on a positive note then I would say the same applies here. They both end with a similar feeling.