In regards to market orders and stops. I dont think you will find many/any brokers that will do it as the Aussie market is pretty illiquid and relies primarily on quote requests from market makers. this makes triggers for stops and finding a "market price" difficult. Good brokers will have a DTR/trader who will receive your order and attempt to gt the best price they can for you so if you are buying and place your order at a high price (ask or higher) you will likely get filled at a pretty fair price. if you are looking for a low cost DIY broker, I know all orders placed with commsec go through a DTR/trader. Not sure if etrade do it.
Regarding trading platforms commsec use a branded version of iress which is pretty good. If you trade frequently enough its free otherwise you pay a fee.