Which is a better option? Topping up CPF account for Tax rebate, or partial refund to CPF the amount used for housing loan?

Yes, you can put cash back into CPF and specifically to return (in full or in part) the amount used for property.

This is also my recommendation to you because:
-every dollar you take out of CPF misses out on the 2.5% risk free interest that "government" gives your CPF.
-every dollar you take out of CPF later comes back to bite you as "accrued interest". In street talk, you will lugi at 2.5% a year.

• put the above 2 points together, it's 5%pa improvement for every dollar you do so.
• compound it actually.

Putting back your CPF used for property should be done as soon as you comfortably can because it's a solution that keeps giving back to you.
Putting cash to SA is the next better solution because it's a 4%pa improvement for every dollar, and a one time tax reduction.

Let's do some maths.

Accrued interest are amount you will earn, if you leave the money in CPF. That's incurring 2.5% loan imho (which you can waive later on).

Tax Relief is immediate saving of 2% up to 22%

CPF RSTU is a 4% interest or If you do Voluntary contribution, it's a 2.8% to 3% interest.

If we add up tax relief and interest rates, my humble opinion is CPF RSTU + Tax Relief is better than refunding.