Should I transfer OA to SA to reach FRS?

I personally think there is a way to optimise. But

Transferring depends on whether you

(1) need the tax relief offered by the SA top-up (if no need, then just transfer)

(2) for OA, there is more flexibility to invest the 2.5% in Endowus and other providers

(3) Is SA shield something you would much prefer also? (Then hit FRS asap to make it work), and top up the remaining to RA after 55 (for SA shield and RA to work hand in hand).

As other commenters said, you can even transfer to your parents etc. I would do SA transfer in this manner.

Parents, then self, then kids. Liquidity is something that people did not consider much, but i would because there is no further advantage to topping up your kids and you deprived them of the tax savings in the future,

while you have liquidity advantage to your parents and personal 1.

I like planning for balance with returns and change of plans in mind.

Maybe leave 3-6 months of housing installments for buffer, and transfer the rest to SA.