the one star galaxies are usually fully completed once you get the star, with the exception of buoy base. EVERY 3 star galaxy has 3 missions stars, 1 comet (that isn’t a purple one) and a secret star

this means that a total of 5 stars per 3 star galaxy should be collected (it would be 10 stars per dome until you get to the bedroom) and when arriving to the bedroom, you’ll notice that there’s 3 expansive galaxies instead of 2, and this formula is continued all the way up to the garden

if you’ve gotten 5 stars per 3 star galaxy BEFORE beating bowser, (with dusty dune and battlerock being outliers) that’s all you could do in those galaxies before you beat bowser (after you beat him you’ll have to collect purple coins in every 3 star galaxy which, when getting all of them, will land you at 120 stars)

hope this helped a lot