5) What happens if I invest without exchanging the currency on a margin account
You can trade on overseas markets without exchanging your NZD to USD in a margin account. However, a margin loan is created to fund the purchase, secured by the assets in your account and you will be charged interest as a result. For more information on the financing interest rates please go to https://www.tigerbrokers.nz/commissions/others_fees/financing.
You should closely monitor margin requirements at all times, particularly for positions denominated in foreign currencies due to fluctuation in the NZD and the value of the underlying position which can cause a margin deficit.
Refer to the FAQ on Pros and Cons on Margin account to understand how a Margin account works.