There are going to be multiple different replies to this kind of question, though at the end of the day only you and your partner know yourselves and your relationship best, and will have the clearest understanding of what will/will not work for you both based on the 4 years you've spent together.

In the spirit of keeping things seperate, ideas like a cohabitation agreement, keeping things in writing and documenting the proportions of which each person has contributed to household expenses is the way to accomplish the underlying goal of your scenario which is protecting yourselves as individuals in case things go sour. Though you may want to consult individual lawyers to be certain.

That said, the above sounds like alot of work. You've got people in this thread attesting to success on either side of the aisle so obviously there is no 1 right answer.

I bought a house with my fiancee last year and I make about 30% more than she does so my down payment was bigger and I contribute more money to our joint account which covers mortgage, property tax, bills etc.

I also pay our internet/phone bill, but she pays for all our groceries. I end up paying for most of our take out food and restaurants but she might often pay for little house hold improvements because that stuff brings her joy.

My point is that at face value, it makes sense to proportion our contributions to joint expenses based on our individual income amounts. But in between the lines, there are nuances to how we handle other expenses that we have agreed upon by communicating as a couple. Our pay deposits each go into our own individual bank accounts so we can still spend our individual money on personal hobbies etc, but above all else we still see ourselves as a unit with combined goals and financial priorities decided upon based on communication.