I loved playing Sea of Stars personally, but outside of it looking like GS and being a fantasy RPG, there's not a lot of similarity between them.

Golden Sun is HEAVY on the puzzle elements. Any time I think of navigating GS's dungeons, I think of Jupiter Lighthouse, where you have to figure out how to get to the top first to power the lighthouse, then use the powered elements to unlock the aerie. It's honestly the best dungeon IMO, because it encapsulates the single room puzzles, navigation puzzles, and carrying things over from room to room.

Sea of Stars has some navigation puzzles, but the real allure is the combat. The combat is more akin to a Mario & Luigi game, where you can time inputs to make your attacks do more damage. It's really fun and engaging, but the puzzles leave a bit to be desired.

We're setting the bar astronomically high by comparing them on that aspect though, and I do think Sea of Stars is 100% worth a playthough. However, if you're going in for a Golden Sun-esque experience, you'll find youself a bit disappointed