We have a joint account but we also have our own individual accounts. The joint account is for emergency savings and paying the big bills, like mortgage/car/utilities, and we both put money into it each paycheck to cover the bills and increase the savings.
But anything in our personal accounts we can't see and don't monitor (I don't need to know exactly how much she spends on planners and crafts, but I know it's a lot, and she doesn't need to know exactly how much I spend on board/video games, but she knows it's a lot).
We also put money into our 401ks (I max mine out, she's getting closer to doing so) and I do additional investing on my own account, which I let her know how well it's doing every once in a while. I would love for her to do more investing besides 401k, even if just a little bit to get some understanding of how it works, but she doesn't want to have to think about it, so I handle it.
Periodically we'll have discussions on recalibrating how much to put into the joint, or some months we'll have the 'this month has more expenses than usual, we should probably go out to eat less and buy less things this month', but that's about it.
Seems to work out pretty well for us.
