Which two accounts should I use for Savings and Expenditure?

I currently have two accounts - POSB Passbook Savings and DBS Multiplier.

The POSB account is barely used. The DBS Multiplier is my main account, and I'm trying to earn maximum interest by hitting the 1) minimum spend on credit card, 2) credit salary into this account, and 3) investments.

Another Seedly article (https://blog.seedly.sg/working-adults-allocate-...) recommends to having 3 separate accounts for savings, expenditure and wealth. Savings and wealth can be combined into one account, so that's not a problem.

But as my expenditure consists of both cash + credit card spending, of which credit card spending is required to earn max interest in my DBS Multiplier account, how should I best separate my two accounts (Savings + wealth DBS Multiplier and Expenditure) and which accounts should I use?