Should I use more Cash or CPF, to reduce the loan amount?

Your financial situation, current and foreseeable future must be professionally and personally analysed before you make large decisions.

In Singapore’s context, home mortgage loans hover at ~2% in 2025 and peaked ~4.5% in 2022 during higher economic volatility.
Cash and CPF (specifically Ordinary Account contributions) when placed in a low risk venture, like fixed deposit accounts often yield the same if not more than (current) mortgage interests rates. On top of that Singapore is often ranked as one of the lowest mortgage interest rates in the world (Japan topping the list).
These combined factors usually mean cash and investable CPF amounts do yield better returns than the costs of borrowing for your property.

On the other hand, if the opportunity gains, costs and work are not top priorities, reducing loan amounts means you reduce your interest costs and stay debt-free!