We’re in a very similar situation to @browniesundae with b/g twins just starting sophomore year, one on quarters and the other on semesters, one with a full ride and the other without. Completely agree with the challenges that the different schedules create, the biggest issue has been the cabin fever in September waiting for the fall quarter, after the other has gone off to college.
Our decision was to give them the same amount of 529 money and let them choose how to use it. D will have a lot left over for grad school (or a house downpayment, etc.). S not so much (although he chose to attend the cheapest school on his list, which just happens to be the highest ranked also, so he still has all the costs covered). But they knew the situation going in (when picking where to apply to) and they are both happy with that.