Your questions about SoFi Hong Kong are answered here

We currently support the following order types:

• Limit Order: A limit order is an order to buy or sell a stock at a specific price or better. A buy limit order can only be executed at the limit price or lower, and a sell limit order can only be executed at the limit price or higher. A limit order is not guaranteed to execute.
• Market Order:Currently limited to sell orders only for Crypto. A market order is a buy or sell order to be executed immediately at current market prices. As long as there are willing sellers and buyers, market orders are filled.