As for how all the other episodes are ones that matter to the plot, it turns out that there is no one major plot for this show, but multiple. At least five, to be precise.
- The development of Starscream and his relationship with Megatron
- The activities of MECH
- Airachnid's history with Arcee
- The development of synthetic energon
- Unicron's awakening
The second has but 3 episodes right now (9, 16, 17)
The third has 4, two of which are shared with the first and second (12, 17, 18, 20)
The fourth has but only 2 (21, 22)
The fifth and final, consisting of the last few episodes of the season, has 4 (23, 24, 25, 26)
And within these plots are little subplots interwoven in, such as Bulkhead's rivalry with Breakdown (10, 16, 18) and the mother/son relationship between June and Jack (2, 17, 18), among other things.
And, who knows? From all we know, the Scraplets may prove to have a significance later on. And we know that Wheeljack is coming back at some point, so his episode may wind up being more than filler at a later point.
As for the racing episode, well, hey, Knock Out needs some love, right? Though, here's hoping if Vince ever shows up again, it'll just be in the background.