Good choice.

Some use. Some don't. I do. Cause it's cheaper for me Vs using sg stock brokerage.

Of course you can. Like I have written many times.
1. Open sg bank account preferably cimb sg ,(as no lockup fees). Mine only have SGD0.10 inside
2. Open money match or Sunway money.
3. Use money match or Sunway money during normal working days to send RM to SG bank account. You will save lots as both of them provide close to money changer rates
4. Once SGD available in your SG bank account, deposit the money into Ibkr for free using FAST transfer.
5. Now you can convert the SHD into almost any currency at USD2.00/conversion using real time market rates. Rates you normally won't get even if you are a priority customer.

You cannot open so many account. One account per ID (NRIC)unless you are doing joing account. You know right one account let you invest practically anywhere?