At 55 years old, after meeting the retirement sum, the excess funds will continue to remain in the OA/SA or will also be channeled to the RA?

Example:
OA $100k. SA $100k. RA $0

Total $200k.
Assume FRS $176k.

once hit 55, you will receive $200k - $176k = $24k.
OA $24k (you can withdraw this). SA $0 RA $176k

Upon reaching 55, only FRS / At most ERS will be transferred to the RA account.

Order of Transfer SA of account Top up monies Ordinary Account.

So if you hit FRS with SA account, likely it will be wipe (unless there is leftover).

You can only draw CPF monies in your OA and SA lump sum..

Anything above FRS will remain in your CPF accounts

E.g IF FRS = $171,000

OA: $220,000, SA:$101,000

turn 55 OA: $150,000 SA: $0 ... RA: $171,000