I am keen to invest in Ireland-domiciled/LSE ETF via DCA/RSP for long-term (i.e retirement as I want to avoid WHT in US market). Any advice to use Saxo or DBS Vickers, considering fees and charges on RSP?

To add on to the above question, due to the limitation of access on SG platform, my original plan is to continue investing on VOO via FSMOne until I achieve 100K funds before switching to IB.
Any thoughts, suggestions on that?

For me I have a Captrader account which is an IB white label that enables me to trade LSE ETFs.