I think the two big things being looked over when talking about 75421 and 75423 are the age rating, and what set numbers they are. They’re both a part of the 8 set numbers (75420-75427) originally intended for 2HY 2025 that got pushed back to 2026. While not confirmed, It’s pretty likely that these sets are intended to be for the Mando and Grogu Movie rather than OT remakes. Since the movie’s release date was pushed back from Dec 2025 to May 2026, It makes sense that all the sets for the movie would be pushed back 5 months as well, just like the Onyx Cinder was last year. That would put these 8 pushed back sets for a release in January, although since only 2 have any information available, I’m guessing the entire Mando Movie wave is intended for a release in March instead.
About the age rating, it’s been over a decade since there’s been any Star Wars set this large for the 7+ age bracket. As of now, the largest LSW 7+ set is the Force Burner Snowspeeder, which has a 45$ gap between it and 75423’s rumored price. I’m leaning towards both sets being locations from the movie, since all Imperial/Rebel ships have been at least 8+ sets in the past decade, barring just the A-Wing. A duel ship pack wouldn’t line up with the age bracket either, since the last 3 have all been 9+ sets.  
My personal guess for these two, is that the Imperial playset is an action sequence from the movie set at some imperial location, while the Rebel playset is the rebel base from the leaked D23 trailer, with a regular A-Wing included on the side to boost the pricetag.