If it is confusing, then you are not ready to trade options. BTW, IG.com doesnt allow options trading.
Your choices are:
Interactive Brokers
Saxo
TD Ameritrade
IB is the cheapest and allows SGD funding, however you are not allowed to buy SGD assets, so you have to either keep your margin in cash or in non SGD assets.
Saxo is slightly more expensive but allows SGD funding as well as allows you to hold SGD assets like ETFs and gives you portfolio margin against SGD assets to trade options.
TD Ameritrade doesnt allow SGD funding and doesnt allow holding SGD assets, you have to wire USD. Also TD Ameritrade is quite expensive at $10 per leg of option trade. However they allow some 100 free trades or something, so while that promo is there you could use it.
I personally chose Saxo.