Top up SA vs SRS vs own self invest?

Actually would suggest doing split between option 1 and 3.

Put max of 7% x your annual income (including current bonus) to put towards the SA. The rest of your savings juggle between cash and ownself investing.

Why option 1 / do rstu?
The frs limit is on a countdown meter. By 50, most people would have max medisave and close to frs. But then they realize its enough for frs but not enough for ers. If you start thinking about doing Rstu after 45, the situation is usually there isn't a lot you can do further with tax benefits for cpf because less time to 55, and you are quite close to frs by then which limits you from doing much. Most people are also not able to consider touching the OA to help form the ERS because they have been using it to pay for property, so either the balance is low, or they still have quite a way to go for the remaining term of mortgage loans.

If you reach frs earlier in life, at 40 or earlier, just let the interest accumulate so that you can hit ers easier and either leave the balance you can withdraw easily from OA or SA. If done smartly, the SA as a 4% pa bank account is a pretty good thing at 55.

Not saying you might not be good with your own investments, but there is really no harm to target ERS and guarantee that cpf life payout which will form the base component of your income after 65. The returns from your own investments etc whether drawdown or dividends will form the non-guaranteed portion of your retirement income.

And no need to like go all-in. Just a bit every year when you are still young goes a very long way, especially when time is on your side (if you have more than 15 years before turning 55).

Why option 3 / ownself invest?
At 7% tax bracket, you don't have to pay a lot in tax. A few considerations - either not married yet, or possible to have more kids. The liquidity will be main driving factor，like the chinese saying, 进可攻，退可守。The beauty is you have the option to go more aggressive in investing when you still single, and commit less / pullback when those commitments start coming up.

Why not option 2?
Frankly I would suggest you do SRS only after you quite close to achieving FRS. Main reason is the countdown mode for FRS, and there is no tax for the cpf route, whereas the more successful you are with SRS, the higher chance you have to pay some tax on withdrawal. So it's not a never, but kind of a bit lower on the priority list.

When your tax rate is like 15% or more, you will also probably do a mix between rstu and srs.
There is no harm to opening the srs account with a small amount to fix the 62 withdrawal age though.

Suggest going for a slightly tweaked version of 2.

Top up SRS to save on tax and retain a certain level of liquidity (with penalty) , and then invest instead in roboadvisors. I think stashaway, endowus and money owl accepts SRS investments. If you choose the highest risk profile with roboadvisors, it's almost all equities with a huge leaning towards US equities. For endowus, you can even choose the funds yourself through fund smart. In your case whereby you are interested in the US market, then you may choose LionGlobal Infinity US 500 Stock Index Fund.

Also you may want to note that all 3 local banks are having promotion ($50 cash/vouchers) in SRS account opening with a $10,000 deposit. But don't let this affect your decision.