Kakegurui Twin is certainly different in terms of plot and mood set up in this show in comparaison with the main Kakegurui show, but it gives a refreshing breath to the series. The ''dark'' mood and the psychological distress we know from the main show is softer in Twin but it still has its intriguing and entertaining side with dynamics games and the relationship between the different characters.
Regarding the quality of this anime itself, several aspects can be highlighted here. The animation style is different from the main series but stays clean and detailed. The OSTs are nice and some of them are just jamming. The VAs did a great job, which isn't a surprise with that whole series.
For people who are saying that Twin doesn't worth it just because Yumeko is not here, Mary genuinely carries this show and the way she is represented here makes that character even more likable now than in the main series.
Of course, only 6 episodes is frustrating but we're talking about a manga spin-off that got an anime adaptation, which is pretty rare. Mappa got several projects and Twin maybe wasn't the main priority but it is obvious that they still put effort into this show, which is in their honor.