From a practical standpoint, we each have our paycheck deposited into a personal account, then set a monthly transfer into our joint account, from which we pay all joint household expenses. We also fund our IRAs from our personal accounts, as well as any brokerage account contributions. We each have a certain amount of free spend, which we use our own accounts for (prevents the need to justify small purchases to each other, ability to buy gifts without spoiling it, etc.)
From a philosophy standpoint, we do all our planning and budgeting jointly. We decide together how much to put in my 401k, his 403b, each IRA, and each brokerage account (not joint only because we both already had accounts open at different institutions). All of these are thought of as joint even if they only have one name on them. Our transfers to the joint account are not equal, but are based on the overarching plan. For instance, right now the joint account is funded almost 80% with 'my' money, because 'his' is being diverted to retirement savings, HSA, and health insurance benefits.
So basically, we have a joint-finances mindset, but a separate-finances execution.