Is there disagreement? Sure. But not at budget reviews - we agree on shared goals. More at the level of "I'm thinking of buying a ..." We check each other. Sometimes we convince the other to not to buy something, other times it's totally OK, and in a few, we compromise/disagree and commit. Each person understands the financial + practical consequences in that last case. The important thing is there's easygoing communication happening before big money actually gets spent (or not spent).
There's no hiding purchases (or accounts) from the other person. Everything is out in the open. There's also "blow money" / "fun money" - a sum allocated to each spouse that they can spend or save on whatever they want - no discussion necessary.
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(I have relatives that are both free spirits, and in that case, it's tough to see so much money flying out the window. But they keep their income up, and they also automate a lot of their savings so they don't have to think about it.)