For Syfe100, it's a very good market entry in the US with low fees, no withholding tax and gives access to top 100 companies. What are the cons for it other than no hedging, 100% equity-based risk?

There is still withholding tax. The dividends you receive is after deducting withholding taxes. As long as you invest in US stock market, there is a 30% dividend withholding tax. Doesn’t matter if you invest through robo advisor or ETF.

There’s a 2 layer fees for Syfe100 portfolio. First, the underlying ETF charges a management fee, many people do not know about this. Next, the Syfe100 will charge another fee on top of the ETF. The fee which Syfe mentioned is NOT the overall fees. Example Syfe 0.65%pa fee is not the total annual fee, you have to add the ETF fees too. Fortunately, it’s still a lot lower compared to mutual funds.